The original bad boy of 3D shooters. Who can deny one of the best games ever made? Quake was revolutionary, for the time it came out. You can laugh at the shoddy graphics today, but nobody had seen pixels look like that before Quake, it set a stanard for the industry, and led as an example for all others to follow.
Besides the graphics, the gameplay was highly addictive. I can remember playing for 12 hours straight on some days. Quake was also one of the first games that introduced me to online gaming. The countless mods and maps that were created for Quake earn it another medal on top of already being a kick ass game.