God, now that I reminisce I realize that the only CoD I REALLY hated was Ghosts.
I started with MW3, and played it, then went back and played all the rest.
CoD4: Honestly a masterpiece, so much fun.
WAW: Too infested with hackers for me to get an honest opinon.
MW2: Very fun, until you got in a game with the grenade launcher and pals
BO: Honestly one of my top 3 so far. I absolutely adore this game. I stopped playing MW3 about two months from BO2's release and fell in love with BO
MW3: I never had any of the problems with it that other people did, because I played search and face off, both insanely fun.
BO2: My favorite CoD, ALMOST flawless in my opinion. If they had just fixed the qsing and lmgs that game would've been super balanced.
REGARDLESS, competitively it was the best imo.
Ghosts: We don't speak of ghosts. It was a boring, slow-paced, placement game.
AW: My third favorite CoD so far, the innovation in gameplay that exos allow is just so much fun. It sucks that the ASM1 and BAL's feel like the only guns in the game.