I played and GM'd in High School and college, everything from TMNT to Vampire, to AD&D, to Cyberpunk2020.
My favorite is probably Teenage Mutant Ninja Turtles and other Strangeness, because it was my first. The rules were simple, but it was fun to roll up a mutant sparrow who could drive around town on a motorcycle, toting katanas and an Ingram MAC-10 submachinegun. I GM'd that game for about a year and a half.
Vampire was another long GM stint, about a year there...mostly because I had a gothy GF and the game was getting me laid.
It's been years since I've played. I don't run in the right kind of circles for that kind of unashamed geekery anymore.