For me CoD has always been a single player game. I loved the first CoD, I think it's the best World War 2 shooter ever made. None of the the sequels even come close in my opinion. Never got into the multiplayer of the game, Battlefield has always been more interesting in that department for me.
BF is as close to a perfect multiplayer shooter as can get IMO. And while BF3 and BF4 are not as much fun to me as 1942, Vietnam and Bad Company 2 I still think it's the best "realistic" multiplayer FPS series out there. CoD (the last one I played was Black Ops) feels more like Unreal Tournament, which is fine, just much more arcade-y than BF.