I actually personally dislike most generic systems. If only because I like many different genres, and I find that a system built to try and encompass every single genre is often on to a losing streak before it begins. The closest I've seen is GURPS, and I still wouldn't use that to run genres outside of science fiction and modern-day stuff, along with a bit of low-level fantasy.

Nonetheless, for me, I suppose it'd be...

GURPS
AD&D
Rolemaster/MERP
Star Wars D6
Mutants & Masterminds