Franz Liszt was the best piano player ever, J.S. Bach the greatest organist ever, but as far as keyboards for rock music, I agree Rick Wakeman gets my vote, Keith Emerson is right up there as well.
I have been trying to get a copy of Illuminations by the Leggat brothers for months, but only found a dead link. They were part of A Foot In Cold Water if I remember correctly.
Peter Hamill?...he did it all.
Hugh Banton....?
Nic Pearn...?
The two in bold were active the longest.
Peter Hammill is the equivalent of Robert Fripp, VDGG is his band, the other two I listed Banton played bass and organ, Pearn keyboards in general but only for a couple of albums in the beginning of the bands career.
I am slowly making my way through their library, but no I haven't listened to that one yet.