COD2 was one of my favorite MP games of all time. Though it did aggrivate me that I'd get 35 kills in one match, and the other three of my teammates couldn't pool together 15 kills for us to win. Happened far too many times. There was no way to get extra ammo in that game other than picking up a dead soldier's gun. And I loved it.
That said, BC2 is hardly anything like the more recent COD games. Yes, there's leveling and unlocks. But there's no stupid killstreak bonuses, no dogs, no AC130's, no nukes. It still requires a fair amount of skill (unless you're using a gustav, then you're just a pansy ass). There's actual bullet drop and travel, not just point and shoot death.
BC2 is really a phenomenal game, mechanically. There ARE some things I'd like to see changed, but, let's face it, it's the best FPS out right now...until BF3. (queue BF3 title music)