I've been a tabletop player since I was 12 with some friends. I believe our first sessions were with Dungeons and Dragons, 2rd Edition (never use, unless you're desperate for some RPing). I'm also experienced in Mutants and Masterminds (a superhero RPG, though it can be virtually used for any kind of game), GURPS (hugely complex, you have to build everything from scratch), and the BESM and Tri-Stat System (both of which are basically GURPS, Jr.).
Note: never try to use BESM d20. The system isn't so bad, but the book on how to play is complex enough that it should be about the size of War and Peace, but its condensed down to 100 pages, making it a pain-staking effort to put anything together on paper.