To be honest I really didn't want to write this review.
The reason is because right now, while writing this thing, I am wasting valuable time that I could spend playing more Left 4 Dead.
I'm very tempted to just say it's great, go buy it and call it a day! But no, I am a professional and will write you a proper review (just so you know, I hate you all).
Left 4 Dead is the latest game by Valve (the same developer who made all the Half-Life and Counter-Strike games). Valve is without a doubt one of the best developers around. They take their times to make things, and their titles always have that special quality a lot of other games lack.
Left 4 Dead is a co-op first person shooter. You can play with up to four players online (or two-player split screen on your Xbox 360). You play as one of four survivors in a zombie apocalypse. How someone didn't think of this game years ago is beyond me, but hey, better late than never right? While the survivors all play exactly the same, they are very distinct characters with unique personalities, and you will get to know them from the dialogue in the game. You and three buddies (or some decent AI controlled survivors if you don't have an internet connection or are just very unsociable) will move through various levels fighting a lot of Infected (their word for Zombies) in order to survive.
Each of the levels are broken up into movies (campaigns). There are four movies with the game, and each can take you roughly an hour and a half to complete. They also begin with cool movie posters showing your username starring as the character you've chosen to play as. And then at the end of each movie you are presented with a ton of stats for how you played, presented as the ending credits for the movie. It oozes style and is definitely an amusing and original way to present information to a player.
The movies are also broken up into five chapters. Each chapter starts with the survivors in a safe zone, where you can collect supplies (weapons, ammo, health kits etc) and then move through the map trying to get to the next safe room. When you enter a safe room, the game will pause and show you some stats from how you played that last chapter; things like who got the most kills, or who took the least damage etc. It's also during this time that the game will load the next level. The load times aren't too bad and are made more tolerable because at least you are given something to read while you wait.
So what are you doing when you aren't waiting? Well going through open streets, dark corridors, spooky houses, corn fields and creepy forests trying to get to your best way out of there. Along your journey will run into a lot of Infected. There will be the immediately visible ones just roaming the streets and standing around, but there are also a lot that you won't see, ones that will spawn around a corner or break through a door (or wall!) or climb over a fence to get to you. As soon as the infected are alerted to your presence they won't slowly make their way towards you, oh no, these suckers will run full-speed to claw at you. It can be a very scary moment when everything is quiet and calm and all of the sudden you hear the music kick in and within seconds a swarm of zombies burst through a door running right for you, and you find yourself surrounded.
Worse still is when the Special Infected get you. While most of the Infected look quite different, there is some special boss Infected that will always look the same and be very dangerous. Left 4 Dead is a game about sticking together and working as a team, and the boss Infected were designed for the purpose of disrupting the team and creating chaos. First you have the boomer, which is an obese wart-filled zombie who waddles around the level making "about to puke" sounds (you learn to recognize the boss Infected's presence by the distinct sounds they make) and has the ability to puke on the players. What this does is temporarily blind you and attract all other Infected right to you. Besides this, the boomer also has a side effect to being shot. When he gets shot to death (he has very little health) he explodes, and if he's close to you or your teammates, he will explode his boomer bile all over you (again blinding you and anyone else nearby and attracting the Infected hoard right to you).
Then there is the hunter who is able to pounce onto the survivors and pin them to the ground. When a hunter is on you, the only way to get him off is to pray one of your teammates will come to your aid. The same goes for the Smoker, which has an extremely long frog-like tongue that it can shoot out and twirl around a survivor, restricting him and pulling him towards the Smoker. They are the perfect infected for splitting a group up, and you can find out for yourself as there is a "versus mode" that allows you to play as the Smoker, hunter and Boomers (more of versus later).
You will also, sometimes, get to control the Tank. The tank is basically the Infected's version of The Hulk. It's big and extremely strong (one punch can send a survivor flying fifty feet). It can also rip up pieces of the ground to throw it at people and absorb a hell of a lot of bullets. The final boss Infected is the Witch, a very deadly woman who usually likes to sit on the ground and cry (her sobbing sounds are very freaky but always a clear indication that a Witch is near by). The thing about the Witch is she just wants to be left along in the dark; that means no flashlights. If you get your light on her, or accidentally shoot her, she will come at you quickly and one or two hits from her will knock you down and soon after that, unless your team kills her first, she will kill you.
Luckily before you get killed in Left 4 Dead you will be incapacitated. This means you will be knocked onto the ground where you can only use your pistols (pistols have unlimited ammunition, a feature you will be very thankful for on harder difficulties) until one of your teammates revives you by picking you up. This is only one small example of how the game promotes teamwork. Another is in healing; you can only carry one med-pack with you at a time and you also have the option you either using it on yourself or your teammate. It's always interesting to see if people are willing to share their med-packs or not.
There are also pain pills that you can sometimes find around the levels. These will only restore 50% of your health and even that is only temporary. The reason you'd want to use pain pills is because as your health gets low there are noticeable side effects. The most important is your character will start to limp, drastically slowing your movement and sometimes it's really bad to be lagging behind the group.
Of course running ahead can be just as bad, as if you get hit by the Infected they also stop you from moving until you get rid of them. This stops players from just running past everything. You have to take your time and move through areas fairly slowly so you don't risk leaving anyone behind. And here is one of the first potential problems with any co-op game; it's based around the assumption that you're not going to be playing with jerks.
When you have a team who all have headsets and communicate well and work together well, you get one of the best, most fun experiences ever. However if you have a team who don't talk, someone who always runs ahead of gets themselves killed etc, it can make the game pretty frustrating. The best solution to this is to play with your friends, because a gaming experience like this with your friends - where you can talk about the cool and funny things that happen - is really what Left 4 Dead is about.