1. Mass Effect 3 by a landslide
2. Halo 4
3. Diablo 3 but only because this wasn't a good year for games.
I tend to stick pretty much to RPGs and RTSs but I wasn't really impressed with any of the games released in 2012. ME3 was insane, I played through all 3 in about 2 weeks doing every mission possible. I might have put WoW MP but since it is an expansion pack I didn't think it belonged.