I love how no one even mentions it be 100% FREE as a reason. Even though it is free, it still stands as such an amazing game that I remember hearing it recently going up on a list of the best games (maybe best FPS games) ever. It is not the graphics or the price that grasps us, but the gameplay, which can be extremely intense and yet can also be relaxed and just for fun, and the communities, and how much effort they put into keeping the game alive and helping fellow players with all their problems.