Co-Op is fine with me, but the game needs to be defined as "Co-Op or not". Halo is NOT Co-Op, seriously, just adding in another player to steal health and ammo is pointless (though I guess adding the option doesn't hurt anybody). But if it is defined from the start as being a Co-Op experience, such as Left 4 Dead, then it's great. You can put a division in there if you want, like how Portal 2 or Modern Warfare 2 both have a single-player and a Co-Op campaign, but you can't interchange the two, and are each designed to work for that number of players. But don't blend the two just because you can. Although I would like to see more not-just-2-players Co-Op. Only game I can think of is L4D, and although Halo and Gears of War and others have 4 player Co-Op, it's just the SP Campaign with 4 people, which DOESN'T COUNT.