I don't remember much about Bad Company 2's story mode (I just remember driving across a huge desert - I do know it was better than 3's or 4's) but its multiplayer had a certain je ne sais quoi about it. Maybe it was the Carl Gustav being a WMD, maybe it was the fact that you could blow up whole buildings for the first time, maybe it was the huge variety in map types (Port Valdez all day every day), I don't really know what but goddamn it was fun.
I do know the Thompson was a badass weapon though.