I started out with (White Wolf's, I believe?) Werewolf, but I can understand if that's not your cup of tea. I continued with GURPS (and still play that in fact; most of the RPGs I've written are based fully or in part on Steve Jackson's work) and recently started to get into D&D (3.0, for those of you who understand the versions). I also play several of my own design, including some based on popular anime (Bleach, Naruto, and Inu-Yasha, all of which are shows I watched fan-dubbed before I watched the American versions, so I have a better feel for how they were meant to be) and one completely original (a post-apocalyptic one with angels and demons and the infernal/divine conflict raging in the background).
So as you can see, I have some experience. I would recommend D&D for a beginner (despite my start), followed by either Werewolf or Vampire (depending on tastes) and finally GURPS for the truly advanced player, though you can play it as a raw beginner (I just feel it's better to have some idea what you are doing before you start screwing with the rules).
On a side note: 400 POSTS! YEAH, BABY, YEAH!! I now feel like I am actually contributing to this community! I think I'll go have a Mountain Dew to celebrate!