Some thoughts on a few candidates I've played.
Sonic Generations: A solid candidate for goty because it managed to finally revive the classic 2D Sonic while at the same time perfecting 3D Sonic. I was a big Sonic fan growing up so this game really made me smile after 15 years of disappointment.
Portal 2: Everything that was great about the first Portal and then some. Entertaining story and wonderfully challenging physics puzzles.
Skyrim: I never got into Oblivion. I heard great things about Skyrim so I bought it on sale. It's tedious, in a word. It has a lot of the same problems as Fallout and Oblivion. There's a sort of mindlessness to it. I'm not sure why I liked Fallout but didn't like this one. Guess I found the subject matter more intriguing. At this point, it just feels like Bethesda is releasing the same game over and over again. Plus the combat blows. FPS style controls do not work well with melee weapons. I also don't feel like I'm getting stronger as I level up. Yep, it's one of those games where the enemies level with you.
Super Mario 3D Land: I'd tie it with SMB3 and even dare say it exceeds Mario 64. It's one of the best Mario games out there, and that's saying a lot. Also one of the few 3D games out there that uses the medium effectively, instead of like a popup book.
Assassin's Creed: Revelations: This one felt shorter, and less in depth than the previous two. It's definitely the weakest of the trilogy. Altair's segments were pretty brief, though they managed to build more on his character in these than all of AC1 did. The formula is getting stale but I still find it enjoyable. I think Ezio's and Altair's stories wrapped up rather nicely at the end.