I can truthfully say the majority of the games I played I played single-player or local Co-op. Actually any game that relies on multiplayer I generally skip because it usually has a terrible single-player. Sure oversimplistic and over-rated games like Cod and Halo might have populations of people playing after the first 2-3 months but then look at the normal games. You'll be lucky to find a decent amount of games going. A year later the games dead. Not to mention most games with multiplayer are just games of playing the same selection of maps over and over again. I'd rather go out and buy a new game with a new story with new gameplay mechanics and with new environments.
I understand not everyone has the money to do this but for me this is the way.