This is my previous favorite game of all time before this generation changed my mind with Fallout 3 and then Skyrim. I must have played through this at least ten times on PC and Xbox 360. The atmosphere and genre go from sci-fi (obviously) to war, to horror, to driving, to puzzle seamlessly. The Source engine blew me away at the time, and even though it was the first iteration of the engine, it still holds up well graphics-wise today.
Portal 2 is second place for me for Game of the Year 2011. The gameplay we all loved from the first game is back, with far more puzzle elements. The humor is more prominent this time around, there are a few iconic characters to carry the narrative, and the addition of co-op (which I was skeptical of at first) is brilliant. The controls for the PS3 version are probably the best first-person controls I've played. I have only played a puzzle or two of co-op, so anybody who has this on PS3 or PC and is interested, feel free to add me. When I'm done with Skyrim (or when it's done with me) I'd love to play some more co-op.
I'm not quite sure what I'm doing yet, so I'm starting with a micro-review of Skyrim. To put it simply, this game blows me away. I'm over 125 hours into my second playthrough, and I can see myself playing this again and again. Bethesda games are buggy as hell, always have been, but the bugs are so easy to overlook when the world is so vibrant and the storyline(s) you make for your character are so compelling.