Setting wise, I've loved Mage (oWoD). Granted, it's our world but really nuts, but still... That may be a function of having good GMs though.
I enjoy the hell out of the SR universe. I'll never give it up.
I like the Paladium/Rifts/Heroes Unlimited setting, but loathe the rules.
The same applies to Synnibar (shut up, I like the setting, damnit. Ridiculous is fine in my world sometimes)
I love the concept of Core, but I've never had a chance to actually play it.
And of course, for pure craziness, nothing beats Paranoia.