I didn't play many games earlier in the year, so I still need to play Assassin's Creed, COD4, the rest of Orange Box (I own HL2 and EP1 on PC), some other assorted 360 games, and buy a Wii to play Metroid and SMG (hopefully in Jan, when things might die down).
That said, my list this year is short, and I based it on how much I can see myself going back and playing the various games on the list after beating them the first time. That's really the barometer test for me.
1. Halo 3
2. Mass Effect
3. Bioshock
4. Crackdown
5. **** Raider: Anniversary
6. Legend of Zelda : Phantom Hourglass