I've been switching between Battlefield: Bad Company and Call Of Duty 4's online multiplayer for the past week. I think Battlefield: Bad Company is light years ahead of Call Of Duty 4, but for some reason, everyone's data is lost, so I can't really level up, unlock guns or anything like that. Therefore, I have to play COD4 to get my level-up fix. COD4's mindless run-and-gun gameplay is pretty fun for half an hour at a time.
