I've gotten a lot of fun out of Farcry 2, despite what people say. It really is nothing but traipsing around Africa shooting people, searching for diamonds, and occasionally progressing a simplistic story, but it does most of it pretty well. I love the buddy system mechanic (Probably not as good as it sounds, it's really just your "extra life." If you get knocked down, your buddy will come up and drag you a couple dozen yards away, let you heal a bit and stick a pistol into your hand. They'll stick around for a while and give some covering fire as well, but you only get this once, until you meet up with them in the safe house again. If you die again, without readying your buddy first, it's game over, back to the last save point.), I think the vehicles, while not great, are at least decent. The drives are a bit much, and you should take advantage of the bus system(fast travel between center and 4 corners of map) as much as possible. If you go through the game playing it only one way, it WILL get repetitive, but if you change your strategy around and try to take advantage of all of the weapons you can get, you'll find there's plenty of ways to do the same mission. One day you may snipe them, the other day you may charge in with a double barrelled shotgun. Maybe an rpg some other time, or just drive on in and slip into the mounted gun to mow the enemy down. Perhaps sneak in with a silenced pistol, charge through with your machete, or hell, just stand back and mortar the whole area. Perhaps one time you'll take the land route by car, or hike up a mountain to get a better angle, maybe the next you'll come in by boat on the river, or swim up to the shore under the water taking the dock guards by surprise.
Again, I'm not saying it's for everyone, but there is definitely potential there if you play it right. You do a lot of the same things over and over again, sometimes even in the same places as you've done them before. There is a lot of world to explore though, a lot of missions to do, especially sidequests, and plenty of diamond stashes to search out.
Personally, I don't play it with the mindset of "I'm going to just play through this game." It's my game that I just have on the side, whenever I want to just mindlessly(Or carefully, if I"m feeling sneaky) drive around and shoot. I really don't even try to keep up with the storyline all that much, what of it there is, all I know is where I can generally find missions if I want them. For me, it's also one of the few games I've played that have made me feel like I'm in a slightly cheesy 80s-90s action movie. I for one, enjoy that feeling.