Really tough
COD4: Spent hours on it, loads of fun. Love the maps, the guns, the atmosphere of the game.
W@W: My first CoD game, always loved it, had a few aspects which others didn't like but I just think it was a really fun game.
MW2: As annoying as it could be, I find it to be quite nostalgic. Also, it gets bonus points because I was sooo excited for it to come out.
BO1: Didn't like it at all really, was OK I guess. Gameplay seemed downgraded from MW2 and it just seemed disappointing.
MW3: A great game, but it didn't really stand out from the series IMO. Fun multiplayer, decent storyline, TOO MANY KILLSTREAKS!!!
BO2: Probably the best CoD yet to be honest, kind of wish I had it on Xbox seeing as all my mates play on that console now... Great maps, great guns, excellent story mode, almost everything that I disliked about the series was fixed in this game. No complaints.
Honestly can't pick a favourite. I don't care what anyone says, I really like the series and I'm not bothered that a new one comes out so often.