Here's my list.
1. Batman: Arkham City; The open-world environment was a great improvement on Arkham Asylum. The combat mechanics are fantastic and I enjoyed putting together combos in the Riddler's Revenge maps much more than AA. On top of that, there was an amazing story and engaging villains, plus much more varied boss fights. One of the few games where I'm done with the main story and went back to finish all the sidequests and try to 100% the game. Definitely my GOTY this year.
2. Portal 2; The puzzles, the story, the humor, everything about this game was top-notch. I just got around to playing the co-op missions with a friend of mine, and they are just as awesome and so much fun to screw around in. Of all the games I played this year, this one will probably be the first that I replay solely to experience the single-player a second time.
3. Deus Ex: Human Revolution; Probably the best stealth game I've played since the Metal Gear series. Also there was enough difference in playstyles that I immediately went back and started playing it a second time just so I could experience all the other cool gadgets and things I missed the first playthrough. The music is also probably the best of the year.
4. Uncharted 3: Drake's Deception; I'm going to be honest, I didn't like it as much as Uncharted 2. However, the latest installment of Drake's adventures had enough awesomeness in it that I still thoroughly enjoyed playing it. Part of the reason I didn't enjoy it as much was because I spoiled myself through media on some of the more epic setpieces in the game, which is my fault, not the game's. Naughty Dog still has me for whatever they come up with.
5. Bastion; This is the best downloadable game of the year. The quality of the animation is well above par. Plus, it has one of the most emotionally-evoking scenes I've experienced in a game in years, and does it without any dialogue whatsoever. The narrator was a cute touch, and the replayability with the idol mechanic makes this a must-play.
6. Bulletstorm; The dialogue is over-the-top hilarious. It shoots past offensive into just plain ridiculous territory. But the solid gameplay mechanics is what puts this on my list. Executing skillshots is just plain fun. Much more engaging than Mad World (which had similar style but fell flat) and the Echoes mode is one of the few score attack modes I replay over and over again. And Anarchy mode is a blast with some friends.
7. Dark Souls; This would be higher, but it wore me down to the point where I just couldn't place it any higher. There are things that make this game amazing and improve upon Demon's Souls, especially the covenants. However, there were a lot more cheap and frustrating parts that, unlike Demon's Souls, I felt were the game's fault and not my own. Still, it says something about the greatness of the game that I kept coming back to it even after I was frustrated beyond belief.
8. L.A. Noire; I thought for sure this was going to be my Game of the Year when it came out earlier, because I was thoroughly engaged and love the game while I was playing it. However, unlike everything I've listed before this, L.A. Noire simply faded from my mind. I haven't had an interest in going back to it, or five-starring cases. The experience was great, but it didn't give me the motivation to replay it. Still a great game to play, though, and I'm glad for it's innovations and trying something new.
9. The Elder Scrolls V: Skyrim; I would be amiss if I didn't put Skyrim on here. I've loved exploring the world, and the magic system is probably the best of any game I've played. But I think my enjoyment of Skyrim suffered from simply overstimulation. There's too much to do in it. Also, most quests end with you exploring some three-level dungeon with tons of monsters and after 50 hours of dungeon exploration I was suffering from exhaustion. Still, though, the enjoyment of random things that happen to me make it a game that has to be in my top 10.
10. The Binding of Isaac; This was a tough call between this and one of my honorable mentions, but ultimately Isaac won out. I'm not normally into roguelikes, but I've poured hours upon hours into exploring Isaac's randomized dungeons. The soundtrack is great, and all the abilities you get are super humorous. Plus, all the bosses have a certain charm to them. Great little game to pick up.
x. Catherine; Almost got top 10, but I decided I enjoyed and replayed Isaac just a tad more. Catherine's mix of puzzle and romance, though, definitely warrants some sort of note. The block-moving puzzles were a lot more entertaining than I would have expected. What surprised me is that the non-puzzle portions were what dragged the game down. The story was amazing, but a little more to do outside puzzles besides talking to people would have been nice.
x Rayman Origins; Forgot about this when I initially made the list. While I can't justify placing it in my top 10 because I've enjoyed every other game more, this one was still a standout hit. Fresh turns on old-school sidescrolling platforming, crisp graphics, and a fun soundtrack make this worth it. Reminded me vaguely of the Donkey Kong Country series, actually.
2010. Vanquish; I wasn't able to post on GAF in 2010, but I played Vanquish for the first time in 2011 and this definitely would have gone on my top 2010 list if I could have made one then. The action is intense, and you really feel badass once you start figuring out the controls and knowing what you're doing. Probably my favorite non-2011 game that I've played this year.