As a drummer I'm inclined to say Jon Fishman. I love his work with JMP, although I didn't really dig Pork Tornado all that much. I think Mike's solo stuff has been the most original, both the Leo Kottke album "Clone" and "Inside Out" are amazing. Page and Trey are great but Jon is the best -- he plays the vacuum no one else on this planet! ;D
It goes without saying that all of them are great, but I have to say that Page is the man. The sounds that he is getting out of his keyboards right now are crazy. But the really cool thing is that he can do that and go back and play the end of Coil on the grand piano like a concert pianist. I feel that the best key players aren't the guys/gals that can play the notes but rather have the ability to use voices to convey the mood of the song and Page is incredible at doing that. He can calm you down, bowl you over, and evoke emotions that make you crave more.
geeeez....fish meat.....NO NO WORD!!! are bad..... ;D trey is definitely my pick mainly because i love it when he interacts with the audience.......i feel more connected with experience.......that is also what i liked about moe in some of their past gigs ive heard on cd.....cant wait to see them.....and after watchin trey and dave jam in africa on vh1 and how genuinely they treat people...how could you not love these guys?