hmmm this is a good topic. So far I would say Borderlands 2 with an honorable mention to Dishonored and Rayman Origins. Darksiders 2 was pretty fun as well.
my biggest disappointment would be Dragons Dogma.... someone put Slay on suicide watch, I tried to like that game... I played right after platinuming dark souls and beating KoA... maybe i had too much RPG.... but i couldnt bring myself to play it anymore.
Game of the year will be between AC3 and ME3. I have a feeling that it will go to AC3 because of all the butts hurt out there over the ending in ME3.
Best MP- going to have to go with BO2 purely because of the scope and the amount of people playing it. I really liked the ME3 multiplayer for awhile and Borderlands 2 sounds incredible as well.