I think one of the dark horses such as Mass Effect or Bioshock will take GOTY awards. Halo 3 is more of the same ol', same ol', as is GTA IV. They may be great games but they won't differ enough from previous versions to win GOTY.
My third choice is SMG.
In order:
1. Mass Effect
2. Bioshock
3. SMG
Or check out my new webcomic: http://selfcentent.com/