Surprised Tony Banks from Genesis hasen't been mentioned yet. Granted their later stuff (80s and 90s) was very Pop Rock orientated, but in their Peter Gabriel and Steve Hackett days Tony was simply brilliant on the keys. So many passages and moods in every song and a superb songwriter to boot.

Honorable metion to Patrick Moranz from the Moody Blues. I believe he had a stint with Yes also after Wakemans departure.