BO2 in my opinion
1)It was an innovative experience in the campaign, shit was radical as fuck, choosing weapons and alternate endings depending on how well you played and shit.
2)Multiplayer was 'ight, lots of new scorestreaks and weapons, had the crossbow and shit.
3)Fuckin' zombies.
Damn everyone here is crazy. Co World at War was by far the best game. I mean it's the game that brought us Zombies. Also the only CoD where you could shoot peoples body parts off. Pubs were dope, campaign was dope and it was just a great game overall.
I have to say MW2 just because of how fun the multiplayer was with friends, just messing around ninja defusing and stuff. But also, I loved all of the weapons in that game. The Intervention, ACR, Famas, Ump .45, etc. That was my first ever game I played when I first got my xbox 360 and got xbox live, thats also probably a big reason I think thats the best cod.