When will Valve EVER make a game that isn't great?

User Rating: 8.5 | Left 4 Dead X360
Left 4 Dead is a game in which you play as a human survivor of a zombie apocalypse. You, along with three human- or CPU-controlled teammates, must cooperate to escape the zombie-infested land and reach a rescue vehicle in four different campaigns. The campaigns each have their own delightfully cheesy title, tagline and poster in a homage to horror films from the pre-80's era. Each campaign contains five levels.
So, the game only has 20 levels that run for ten minutes or less each. The game itself is short. So I certainly wouldn't recommend buying this game unless you at least have someone to play with (or, better yet, you should have Live, so that you can play with three other people). The achievements are fun little challenges that you can shoot for and they do add some decent value. Every time you play the game, it will be modified by the randomly-generated enemies, or by the AI-System called 'The Director' that can change the difficulty, the music, or the effects, just to name a few.
If your team isn't working together in the game, you aren't likely to last very long. You have to work cooperatively and strategically to ensure that you make it to the end of the campaign alive.
The original fun of the game is likely to float your boat, but buying this with the notion of playing it alone will definitely sink it.