TOME is really good, and has a very large overworld which is teeming with neat monsters. It's basically Angband but with an overworld and more dungeons. The goal is the same, but you can't go straight to Angband, you have to progress through a series of dungeons to get better loot. It has lots of special quests in the dungeons to break up the monotony and give good items, like princesses in need of rescuing and assorted mini-bosses. Supposedly there are real bosses at the bottom of the dungeons, but my playing style doesn't let me see them(I go into the swamps south of Bree(I think it's Bree, can't remember) and train as a mage, killing weak naga to level up until I can go after hydra. I get like three or four levels for each kill till like level 20, when I go straight to the orc cave and die being stupid)
Seriously though, it's cool. And if you get bored on the main quest, you can do the super-epic-awesome mode. You make your character like usual, but when it asks for your variation, pick Lost Soul. You end up at the bottom of a 100-floor, very high level dungeon, and have to work your way up. It can actually be a lot of fun, you start with like 50 identify scrolls, so you can very quickly get good gear, and if you find a Quylthyulg(Sp?), it's like 20 free levels, assuming it doesn't own you with summons. Even if you get those twenty-levels, Balrogs and packs of elemental hounds will still smack you down, so you should try to find a digging item fast and head for easier areas. Talking about it has made me want to play it, I think I'll do just that.