I don't understand the popularity of the CoD series multiplayer at all. It's always horrendously unbalanced and full of what seem to be simply poor design choices.
My opinion is probably biased though, as when it comes to multiplayer FPS I really want something that involves teamwork, which the CoD series really lacks. I know they have team based modes but in my experience they've basically been the same as a normal deathmatch mode; every man for himself using the same ridiculous builds to get as many points as possible, except that you can't kill half the players since they're on your team
Best FPS of 2009 for me was Killzone 2, fantastic MP component.