Left 4 Dead

It is only 2 player split-screen offline, and 4 player co-op on XBL or over system-link. If you don't have additional players to play with, they will be filled by bots.

In order to do 4 player co-op you have the be online. Now if you wanna play with a friend on the same xbox it will be you and your friend with 2 ai partners.

you cannot play 4 players on one single xbox. To get 4 players together you can either play through xbox live with friends or strangers or system link together 4 xbox 360s with 4 TVs through a router.

For the campaign you can have 2 splitscreen players max, or you can go on xbox live and have a 4 player campaign session. also, there will be a versus match with 8 players compatible i believe, 4 players being survivors, and the other 4 being special zombies, but im not sure about number of people in a versus match.

2 player offline,4 on Xbox live.

You can still play spilt-screen in all modes of Xbox live, with two people being the max number of players on one Xbox.

You can do four player offline co-op campaign as long as you have system link other then that offline you can only have 2 players max in campaign.