toss up between modern warfare 2 and ghosts, had a lot of good time with ghosts with the community, but cant deny the excellence of mw2, after all it is the game that made me choose CoD over Halo.
Call of Duty Black Ops. Was my favorite because the multiplayer was the best for me and you cant even mention how awesome the zombies were and the guns were just fantastic, favorite weapon m16. I wish they would remaster that game. i would totally get it. im really not a fan of the jumping/
Modern Warfare 3 because I really liked the maps, guns, overall feel of pvp in that game. Sure i wasn't good but i loved playing that game i'd spend afternoons having a blast playing that game.