Okay, I suppose I should go under the assumption that a) I'm not already playing something(s) and have both the time and inclination (determination, even) to play an RPG, and b) I'm playing and not GMing (which, most often, is not the case).
In that case, I might try anything, even something I'm not keen on, though, because of recent experiences, I probably wouldn't play high-level 3.x. I also would tend not to play a game like Rolemaster with all the charts and rolling simulationist stuff.
I probably wouldn't last long on a 2e game before the hate returned, either.
Oh, or a LARP. I don't swing that way.
Without the assumptions from the first paragraph, it'd have to be something darn awesome to even consider.