alrighty...i have been playing rock keys for thirty years, and while there are lotsa great ones out there. but ya gotta distinguish between great keyboards (ie Steve Winwood plays an amazing Hammond B3, but is just ok on the piano). So here is a list of pianists...in no particular order. some of em u might not heard of, but rest assured, they are amazing sessions folks:
chuck leavell (plays for stones, Train, etc). incredible range
bruce hornsby (amazing chops, can play any style)
Elton John (yep, behind the flash, the boy treats the instrument for what it is,percussion)
Keith Emerson - I would give an appendage to play like him
Richard Tee
Dr. John - New Awwlins, but can play rock
Professor Longhair - The father of rock piano
Roy Bittan - Springsteen's pianist. Classically trained, and incredible blend of that and old school influences