41. Left 4 Dead 2
A brand new group of survivors are back to fight the good fight, and by that we mean mowing through crowds and crowds of the shambling flesh-eaters. This is a brand new saga with new characters to get attached to (or sigh with discontent if you can't play as your favorite) and hundreds of zombies to keep you occupied. And if you play your cards right and grab the DLC, you can have both groups of survivors meet up, once and for all. Sound like a lot of fun? It would be, if life as we know it hadn't been completely obliterated.