Exalted - bought it, read it, need to run it (and love it)
Fading Suns - the closest thing to my beloved WH40K - never played, always wanted
Deadlands - great concept, great storyline, not bad mechanics, but my players just don't seem to be hooked by it...
Vampire Dark Ages - I'm big fan of this setting, but never had a chance to play
Call of Cthulhu - great game, played few times, want more...
Star Wars - either d6 or d20. Doesn't matter...
Dark Matter/d20 modern/d20 future - plan to run a cross-over
Of course there are hundreds systems to be played. These are the top of my list.
Regards,
d.