Summer, 1989: Watched my brother play Shadowrun, 1st edition, on a picnic table in the back yard. I was 9 years old. I remember someone asked what was in the trunk of a car and the GM said "a bazooka", and it blew my mind.
Winter 1990: Played as a PC in my best friend's D&D game. I honestly don't remember if it was Basic or AD&D. I remember we rappelled into a temple through a skylight.
1991-2000: I DMed a lot of AD&D for my friends. Mostly it was those little brochure-sized modules you could buy at the comic book store, but also some of my own campaigns. I played in and ran some Play-by-Forum and Play-by-Email games during the last few years of the BBS scene, and the first few years of the web.
Around 1996, I went to my first gaming convention, and played Amber Diceless for the first time. I also played someone's homebrew old west RPG, and it was one of the funnest things I've ever played, but I cannot for the life of me remember what it was called.
The friend who'd introduced me to D&D ran a long Call of Cthulhu campaign.
2000-2004: In college, I didn't play as many games, but I did run a Victorian horror campaign in a system called The Mirror for my friends, whenever we were all home on vacation. I also played in a modern horror-themed PBeM game for several years, with a GM that went on to become a reasonably successful filmmaker. I won't blow up his spot, but that was a really fun game.
2005-present: Every week, I run a 4-hour session for 4-5 players at my home. It's been D&D, Deadlands, Pathfinder, Reign, Star Wars, Trail of Cthulhu, Godlike, Savage Worlds, and a number of smaller one-shot systems. Right now, I'm preparing a 13th Age campaign.
Since around 2008, all the fantasy campaigns have been run in the same campaign world my players and I have been building together.