Zombies themselves don’t seem to be much of a creature of horror anymore. Is it even possible for something to remain scary through constant exposure to it?
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.
For all of its pluses, nearly all of Left 4 Dead’s ability to scare was built into the dynamics of play. This is usually a boon for games, matching their ideas or story to how they play. But once players looked beyond the façade of the zombie apocalypse, the dynamics proved not to be so terrifying. When you have four people all working towards the same goal, things can’t be as scary. You aren't alone, and you aren't helpless. The game promotes cooperation and relying on your teammates for help. It is often more advantageous to use a med pack on an ally than to keep it for yourself. Players learned that altruism towards their fellow players helped them succeed. That and any attempt to go alone is soon met with a quick and overwhelming zombie death.
The game also couldn't keep up with players learning the system. The AI director creating new experiences every time sounds like a great idea, but it is actually limited in what it can do. It can change the types of zombie that attack and what doors they burst through or how many it sends at any given moment, but it does so to meet certain parameters. Namely, the level of challenge that the players are experiencing. The players eventually got into a rhythm as they figured out how the AI director worked. Eventually they could anticipate how the game could respond most of the time with what was suppose to be procedurally generated zombie horde and behavior.
Over time, Left 4 Dead ceased to be scary. It retained all the trappings of a horror game, but none of the sting. The sequel was equally hampered upon release and had to overcome a player base that was already used to the major mechanics and dynamics of the game. New enemies and new levels changed up what we thought we knew for a while, but eventually through repetition the new game ceased to be scary as well.
Familiarity breeds apathy. Over time, things that were truly terrifying no longer have the same hold on us. Vampires and werewolves have been neutered in terms of their original effect on our culture as European folktales and later Golden Age Hollywood horror movies. Now they are sex symbols, things to be desired not shunned and feared. Even Cthulu, the great Lovecraftian Elder God whose very existence could make a man go mad has been overexposed in our culture long enough to be chibi-fied and turned into plushies. Is it even possible for something to remain scary through constant exposure?
Back to Left 4 Dead. Part of the problem with it was that it only possessed the surface level elements that allowed it to be called horror. The game itself wasn't built to fully encompass horror, since the abundance of bullets meant you always had agency, a way to fight back. It lacked a concrete narrative meant to cause terror through ideas instead of play. It lacked big changes that upset the status quo and really screwed with the player’s mind. Having guns and having agency isn't itself a deal breaker. F.E.A.R. accomplishes the same thing pretty well. The truly scary parts of the game aren't affected by the agency that the game affords you. You can’t shoot Alma and bullet time isn't going to stop the nightmare sections that change the rules of the game.
Zombies themselves don’t seem to be much of a creature of horror anymore either. They’re the apocalypse de jour, a means for society to completely break down so that we as a culture can explore the interesting bits of our psyche. They aren't monsters to be feared. They are obstacles that have certain rules tied to them. So even that connection to horror is cut off from the game. Left 4 Dead doesn't look into the aftermath of the zombie apocalypse or man’s crumbling façade of civility. It is a shooting gallery that takes the least horrifying aspect of the zombie story and stretches it into a game.
Without anything else that could be classified as horror elements, Left 4 Dead becomes just a co-op shooter. Once the new game shine has faded, the game ceases to be scary. Most horror media stops being scary on repeat playthroughs/readings/viewings, but the really good stuff does leave something behind in the audience’s mind. Left 4 Dead leaves behind some stories created alongside friends or strangers, but nothing that could be classified as leaving a niggling feeling of dread in the back of your mind, nothing that could wake you up in a cold sweat in the middle of the night. In the end, Left 4 Dead really isn't a horror game.