Woah, woah.. BC2 might be a better FPS all around than MW2 but MW2 is a great game regardless.
It's gamey. Dolphin dives, nukes, unrealistic shooting, completely hide yourself, riot shields, heartbeat sensors, the killstreaks.
Killstreaks...the choppers...most people would say "just pull out a stinger". why would I have to? It's a first person shooter, not first person airsupport killer.
Also, last stand, the no-recoil guns, the 50cal sniper that can be shot like a sub machine gun, the dual 1887, many many many more. COD4 was genius, pure genius. It was a perfect balance IMO. Many good snipers, good rifles, good everything. The only gripe would be Marty, LS, and again, the 50cal semi auto "sub machine gun" style tactic.