Ok I'll go ahead and post some informative stuff about Torchlight 2, since nobody's asking specific questions, but a couple have commented on the lack of information. Also, playing the first game isn't good enough in my opinion, because the gameplay was very basic and content was very shallow, in comparison to the sequel.
Graphics
----------
I personally love them. I'm not usually a fan of cartoony styles, but they execute it so well that it doesn't bother me. The animations are expressive, smooth, and varied. The color compositions are very pleasant to look at. The amount of detail in the textures is balanced just right, so that it doesn't look too cluttered or overly simple.
As compared to Diablo 3: I felt like Diablo 3's graphics were actually pretty bad. The style was almost as cartoony as Torchlight 2, except it tried to pass itself off as not so by abusing the hell out of heavy-handed atmospheric post-processing effects. Your character seemed to be exempt from most of these effects, making them appear sorely out of place. For the production value Blizzard should have been able to produce, I was incredibly disappointed.
As compared to Path of Exile: PoE has the most sophisticated graphics, with the most dark and gritty style and the most detail. I like its style the best, but it is also the least polished. It definitely has the feel of a work in progress. I expect it to get much better. Right now many of the shaders can use a lot of tweaking, and they're just beginning to incorporate some atmospheric post-processing effects. The finished game will probably look more impressive than D3 or Torchlight 2.
Audio
----------
To be honest, I'm not much of an audio guy. I typically turn game music off and I only pay attention to sound effects so much as they act as cues to what is happening.
Story
----------
Similarly, I have never played an ARPG where the story was worth paying attention to. These games aren't known for their literary feats. There's monsters around causing trouble for people. Go kill them. They've taken things from people. Retrieve the things. There's some important people in danger. Protect/rescue them. There's some ultimate big bad monster behind the whole thing. Hunt him down. Path of Exile is the only one that comes out ahead in this area, since you start out the game washing up on an island beach after being exiled as a criminal. At first, you're just fighting to survive, and it doesn't even begin to hint at a larger story until the end of Act 2, which is all that most people have access to at this point in the beta.
Gameplay
----------
Potions -- Each game has its own take on this mechanic, and it has significant effects on gameplay.
Diablo 3: Holds your hand. Monsters frequently drop health recovery things that prevent you from having to use potions at all. There are no mana/hatred/discipline/whatever your spell-casting resource is potions. You naturally recover that stuff so fast, that you can spam pretty colors all over the screen all day, even at level 1. I honestly don't even understand why they left mana in the game, because they trivialized its expenditure so damn much. At least, this was my impression. Then there's health potions, in case you were still having trouble staying alive.
Torchlight 2: Takes the classic approach to potions. They drop fairly frequently, and you use them fairly frequently. There aren't many sustainability mechanics in the game. I've played up to level 20-something, and found that lifesteal is incredibly rare. There is no natural health regeneration on any character, and I have not found any items with a health regen enchantment. The berserker has some lifesteal abilities, but they are active types and very meager at early levels (like pay 1/10 of your mana to hit something once for less than your basic attack damage and regain 5% of your health). The engineer can summon a healing bot that follows him around and emits a substantial healing aura. Mana is a little more forgiving. It does regenerate on its own at a substantial rate. In fights against large mobs or champion/boss monsters, you will be consuming mana potions. Against normal mobs, you can typically drop a couple spells to obliterate them, and have that mana back before the next one.
Path of Exile: I like PoE's approach the best. Instead of potions, you get flasks. Flasks are items that are placed in equipment slots, just like weapons or armor or whatever. Instead of consuming them permanently, you spend charges that flasks accumulate as you kill monsters. This system has three advantages. First, it gives the developers a much greater control over balancing the pace of the game. Second, flasks can be enchanted like any other piece of equipment. These enchantments can be boosts to the HP/Mana gain, or can do other interesting things like removing status effects or giving you various temporary boosts when you consume them. Third, this offers you more choices for character building. Does your character need more health or mana? Do you use the flask that recovers a ridiculous amount of health or the one that gives you a temporary speed boost? Or maybe you want one that recovers a very small amount, but triggers automatically when your health falls below a certain threshold, saving your ass in a sudden emergency?
Combat/Character Building/Pacing/Difficulty
Diablo 3: I admit I didn't play for that long... but it felt like a spam fest. This is actually the main reason I couldn't stand it, and quit so early. There was no resource management. No tough decisions. No strategy. Just spam pretty colors all over the screen and watch stuff die. Every ability seemed to be some variation of pretty color spam, without any substantial reason to ever choose one over another. I also absolutely hated the restrictions on equipment usage between classes. It drove me insane that I couldn't equip anything but a bow on my demon hunter. Improvisation early game is one of the most interesting things in this genre, in my opinion. I loved starting new characters in Diablo 2, because I'd always end up doing really wierd stuff early game based on what rare equipment I found that didn't match my class when I hadn't built up enough class specialization for it to matter.
Now that the game is released, I'm seeing testimony that the game does get more difficult and interesting. It seems to me that Blizzard just fucked this up big time. They let people play that open beta weekend, but only gave access to the least interesting content, which gave a lot of people the wrong impression and chased them away. I only learned yesterday that you ever actually get any real choices when you level up, but it takes a couple hours of gameplay to get there. The first several levels, everything is selected for you. Attributes are assigned for you throughout the entire game. So after a bunch of reading and talking with friends who own the game, I only see two ways that you can customize your character in Diablo 3. Your abilities are mostly chosen for you, but you get to customize them rather extensively. I'm not sure just how much impact your choices here actually have on how you play the game, but my impression is not very much. I'm pretty damn sure it's all style and no substance, since everything is tied to your weapon damage anyway. Then there is equipment, where your choices are severely restricted according to your class. Yeah...
And you know... I've seen a ton of debate recently on the topic of character customization. There's a very large camp that says choices are illusory anyway, because people will always crunch the numbers and produce mathematically perfected character builds. You then have to follow those builds or you're a worthless noobish scrub, whose character will eventually fail and have to be re-made. I understand this argument, but I really don't care. Without experimentation and risk of failure, you're not so much playing a game as you are following directions. I don't understand what kind of enjoyment or satisfaction people get from this. I really don't. I enjoy coming up with my own non-standard styles of play. I don't care if that means I can't PvP with the best or solo act 5 inferno. The added difficulty and uncertainty in how far I will be able to go is what makes it fun. There's no such thing as winning when there is no chance of failure (this is why I play hardcore). Instead of presenting a ton of options and letting the community produce the cookie cutter builds, Blizzard decided they would pre-empt this by restricting everything so that the player is not even allowed to deviate from what the cookie cutters would have produced. This is not what I call a solution, it's a resignation. NOT the way to go in my opinion.
So... moving on...
Path of Exile: I've played through the entire PoE beta, up to halfway through the second difficulty level on hardcore mode. It's substantially more difficult than Diablo 3, but still fairly easy. I have died a few times, but never unexpectedly. I have yet to lose a hardcore character. Nothing is really hard-hitting enough to surprise. Bosses don't feel like unique events. They're just slightly tougher monsters. For all the things I like about Path of Exile, I have to admit that the gameplay is very dry. You do have to be careful. The game doesn't hold your hand like Diablo 3 does. But so long as you are careful, there isn't that much challenge. Supposedly, the highest difficulties get ridiculous, though, so I don't know. The pacing is also kind of annoying. You will be making constant town trips.
But... the shining core of PoE... the character building. This game has by far the most versatile and complex character building I've seen in an ARPG. First, it is a class-based game... but not rigidly so. The whole thing is based on a "Passive Skill Tree" which you can view
here. If you've played FF10, it's much like the giant node map that you leveled up with there... except much larger and more varied. Your choice of class has only two impacts on gameplay -- your starting attributes and your starting point on that passive skill tree. This makes it easier to build towards stuff related to your class, but not prohibitive for you to deviate into something entirely different. There are also no active abilities on the passive skill tree. They only effect the "feel" of your character. This is where you buy your attributes, which typically make up the paths between major nodes that substantially change the nature of your character. Many of the major nodes are really interesting, such as dropping your HP to 1, but raising your energy shield by 80%. Or you can turn all of your energy shield into mana. Or you can do both, and have a 1 hp character with shitloads of mana. My impression is that no character can possibly cover even 1/5 of that map, so it's really easy to make every character unique.
Everything else, including active abilities, is based on equipment. What you can equip is restricted only by your attributes, and the passive skill tree is designed to give you plenty of opportunities to put points in every attribute, no matter where you are on the map. So you're offered tons of freedom of choice, without being able to do everything at once. Your active abilities are gained via gems, which you are granted a handful to choose between as a reward for most quests, but are also rarely dropped by monsters. These gems are socketed into equipment, but not permanently. You can move them about freely between all of your socketed stuff, or just place them back in your inventory. So sockets on equipment is
really important. You will often find yourself agonizing over some item with really awesome stats, but none of the sockets you need. Sockets can also be linked between each other, giving you the option to add support gems that augment your active abilities with extra features. Each of these gems starts at level 1 and gains experience proportional to your character. At every level, the attribute requirements to use that gem go up... so your tanky melee marauder has the ability to equip elemental nukes, but he simply won't be able to level them up very far.
There are several more interesting aspects to character building in PoE. The number of significant variables that define your character is astounding. I think I've covered enough of the basics that you can compare to...
Torchlight 2: First, I'll cover character building, which is Torchlight's weakest gameplay aspect... but it's not that weak. It's certainly still way beyond Diablo 3. It's very straightforward, even if there are a lot of really clever touches to it. When you level up, you place 5 attribute points. The attributes are very standard and mostly do exactly what you'd expect. The two most interesting things are fumble and execute, which I can explain if anybody wants. Attributes are also, of course, the limiter on what stuff you can equip. This is where they have another clever mechanic, though. Equipment is limited by level and/or attribute. What this means is that everybody gets access to an item at a certain level, but they can get access to it sooner if they specialize in the right attribute. It's a small touch that goes a long way. You also get one point to place in abilities. It's also worth noting that your character has more total equipment slots than in any of the other arpgs (12 total, if counted correctly off the top of my head). There's a wide range of abilities to choose from, granting access to very different playstyles. The choices here are really difficult, because it encourages very heavy specialization. I find myself putting all of my points into only 3 or 4 abilities with each character, out of the 20-something you unlock by level 14.
There's also spells, that are separate from the character abilities that you choose at level up. You 'learn' them by equipping them, but unequipping the spell destroys it, and you only have 6 slots for them. There's no limitations on who can use what spells, and they're quite varied, from healing to blasting to passive buffs. Pets can also equip and use spells, which is really awesome.
Pets in general are really awesome. They're well-balanced to actually make a difference without being able to carry a fight for you. The absolute best thing about them is that you can send them back to town to sell loot and buy potions/scrolls for you. This does so much to prevent tedious breaks in the pace of the game. I seriously appreciate this feature so very much.
Everything else about the gameplay is far beyond the other two games. The combat is easily the most fun out of all of them. Resource management is balanced just right so that you can nuke through minor nuisance monsters, but have to find more sustainable approaches to other encounters. I make sure to always have a ranged attack on every character for this reason (and you are allowed two weapon sets that you can switch between with 'w'), because you very often encounter monsters that you simply cannot stand toe to toe with without guzzling all your potions, even as a melee-centric character. The monsters are very well balanced, so that you often fight several types at once, and each type requires different tactics.
Besides the interesting variety of monsters, combat itself is very dynamic, because all attacks (except claw attacks) apply damage to an area instead of directly to an enemy. This brings an interesting balance to what weapons you choose to use. Atypical of the genre, big two-handed weapons don't do as much damage as one-handed weapons. Instead, they attack in bigger arcs, and hit more monsters. Your attack is focused on the creature you click on and that creature takes the most damage, but everything that gets touched by your weapon in the attack animation is effected. Ranged weapons also make use of this mechanic, with bows and pistols being single-target, but shotguns and cannons targeting a cone. This heavily factors into your tactics. This stuff also applies to monster attacks, making mobility a huge advantage. If you can dodge out of a big monster's attack, you wont take damage from it. There are mobility spells in the game that further allow you to take advantage of this - not as many as I'd like, but they're there. It puts a lot more "Action" in "Action RPG". There are many nice little touches to the whole combat system that I'd like to mention, but this is already TLDR.
I'd also like to mention bosses. They actually feel very special. They are truly noteworthy events. They have huge amounts of HP. I've had a couple fights last more than 20 minutes, when I was playing a tanky character without much damage. On one occasion, I even had to send my pet back to town in the middle of a boss fight to buy potions for me. It's also nice that none of the bosses I've encountered have any regeneration, so that as long as you can stay alive, you will eventually win the fight. Their damage is very well-balanced so that you can melee with them for short periods of time and there's very little threat of being insta-gibbed, but there's no way you can win the whole fight that way. The real threat is the hordes of minions that bosses are constantly summoning. You have to regularly divert your attention away from damaging the boss to attend to all the minions and always keep moving, or you will be quickly overwhelmed. A combination of AOE minion control and focused damage techniques are necessary, and it's these moments where multiplayer teamwork really shines.
Overall, I'm very happy with the difficulty. They give you four difficulty options right away. I'm always playing the highest difficulty in hardcore mode. I've lost several characters, without having encountered anything that frustrated or annoyed me. It was always my mistake. After you beat the game, there's supposed to be a "New Game +" mode, but I have no idea what that will actually entail.
Other Stuff
-------------
The fact that Torchlight 2 is actively supporting its mod community is huge. I don't think Path of Exile will see any modding, because it's being designed like an MMO with "instances". Modding the game would require private servers. Blizzard has made modding illegal by the terms of their EULA. Then Runic goes and releases a full set of tools for their game. Torchlight 1's mod community was decent. There's a few total overhauls, dozens of classes, and hundreds of items and various tweaks to toy with. I expect a lot more from Torchlight 2.
Then there's price. Path of Exile is really good for a free-to-play game, but Torchlight 2 has an incredible amount of content and polish for its price (enhanced infinitely by mod support), especially as compared to Diablo 3.
Edit: And... of course... Torchlight 2 is the only game out of the three competitors that does not require a constant internet connection, which is a criteria that I think more people properly appreciate after this weekend.
I'm going to go ahead and stop myself there. I can't believe I wrote all this. I wrote this at work over a stretch of 6 hours with lots of interruptions, so I hope this came out somewhat coherent and informative.