Left 4 Dead started out as a humble homage to zombie survival films. Valve's multiplayer-focused first person survival horror game wasn't expected to make much of a splash in a market already saturated with similarly zombie-themed games. But clever gameplay mechanics, like when the action was too dull, an AI "director" would unleash a horde of zombies to keep the survivors on their toes, helped make the game distinct. Left 4 Dead 2 has shrugged off the predecessor's underdog status, and has now become an expansive, varied, and beautifully atmospheric standard for which all other survival horror games are judged. It's no wonder some consider it the scariest video game of all time. Forget Resident Evil or Dead Rising, there is nothing like going through a creepy old sugar mill with your three friends, low on health, and knowing that at any point one of you can be dragged to your death. The only feeling better, perhaps, is being the zombie that does it.