AC2, most immersive storyline and interactive gameplay. Best game I've played in years.

COD6 was horrible, it is so imbalanced and people always camp...always, the m16 is still a whore gun and everyone uses it, the famas is just over powered.plus once people try to "snipe" they never go for headshots. p.s thermal scope makes i even worse

Though i would probably like AC2 better, I voted MW2 because of the multiplayer.

As most people, I also say AC2, or ODST. ODST is by far better than Halo 3. It has an amazing story, better graphics, and it comes with all that "legendary" Halo 3 multiplayer you always hear about (although it sorta disappeared since MF2).
Then AC2. I enjoyed AC somewhat. It was a sandbox kind of game at the most. The only reason I did missions was to find out how it ended, as the missions before the missions were boring, plus the unskippable conversations. Anyway, AC2 removes all of that and adds more, making it a perfect sandbox game.