Left 4 Dead is ostensibly a horror game. Upon its release, it was called the first true zombie apocalypse game because it actually created the feel of a zombie apocalypse. You are one of the last four people alive and have to make it to safety. Everything is so thoroughly destroyed that you can do nothing but move on. Even the safe houses aren’t places that you can survive. It has all the elements that make a good horror game: moody lighting, a thick atmosphere, unrelenting tension, a sense of danger, and a dwindling sense of hope that is finally replaced by despair. So, why doesn’t it stay scary?
Over time, Left 4 Dead ceases to be frightening. In the beginning, even in co-op, the game was terrifying to play. People didn’t so much speak commands as scream them out in terrified surprise. People could play the same levels over and over again and get different experiences thanks to the Valve’s AI director tailoring the journey depending on how you were doing in an effort to keep the tension high. But again, the terror didn’t last.