I didn't care for Alan Wake. The gameplay was SOOOO effing repetitive and that alone takes it off a GOTY for me.
Mass Effect 2 was good, but the general story was very underplayed here and I didn't like that. They focused way too much on the side stories for each character in the team. That takes it off GOTY for me.
Halo Reach is absolutely epic. The difference between Halo 2 and 3 was minuscule, but 3 to Reach was extremely different. The story was soooo much more epic feeling and the multiplayer kind of speaks for itself. Def GOTY contender for sure. My only gripe is the Forge editor maps can't be shared online.
Red Dead Redemption was also extremely fun. The story sucked complete ASS after you returned to your family and it definitely started WAY too slow, but the rest of it was a lot of fun. I would put this under Halo: Reach.
Bioshock 2 = Bioshock 1 w/ multiplayer and far less provocative storyline. I enjoyed the game, but def not GOTY for me.
I think the game that truly deserves GOTY is Starcraft 2. The campaign was incredible in story, graphics, and features. The multiplayer, while similar to SC1 in play style, is extremely fun and still feels fresh, and the immense map editor has already turned out some amazing games. This game checks off every category with flying colors, whereas the others (except Halo Reach) fall short in some categories.
In the end it'll be between Halo and SC2. Fallout New Vegas, I suspect, will be a long Fallout 3 expansion.