Does the original Left 4 Dead support local co-op for 4 players? Not using XBox Live but physically sitting in the same room looking at the same tv.
Left 4 Dead and its sequel both support 2 players maximum in local co-op mode on the Xbox 360.
You can, however, join a campaign game lobby with a team of two local players and round out the game with 2 more. Alternatively, you can System Link 2 Xboxes with 2 TVs and play 4 player in the same room (assuming all of this gear fits in the same room ;) )