Oh dear. I was waiting for this thread to turn up - I've given up arguing this on youtuber comment threads. [Warning, this may become a very drawn out analysis!]
Here's my two pence:
1st Place: Keith Emerson (Emerson, Lake and Palmer) take the crown for his combined technical brilliance, compositional originality and the fact that he tours with a Modular Moog and sticks knives in his Hammond. Special note for me as his music got me playing classical again.
2nd Place: The Caped Crusader, Rick Wakeman. For all round awesomeness and ordering a curry on stage with Yes. And all those keyboards. Combine his right hand with Keith's left and you have the ultimate keyboard player.
3rd Place: Tony Banks (Genesis) For services to the Mellotron (listen to the intro to "Watcher of the Skies". Then listen to it again. Bathe in the washes of sampled brilliance. Repeat.). Also for Firth of Fifth. Need I say more.
Honourable Mentions:
Rick Wright: Doesn't strike many people as technically brilliant, but as soon as you remove the keys from Pink Floyd, it becomes very bland indeed. In particular listen to early Floyd where it is impossible to distinguish keys from guitar.
Jordan Rudess: Oh alright then... I've only recently started listening to Dream Theatre and while there's no denying his technical skill, his compositions let him down - they are essentially just the keys parts from DT songs. Such a shame, since he is one of the few people who can push the Oasys and K2600 to their technical limits. I might try some LTE...
Jean Michel Jarre: For inventing Ambient and Dance music as we know it. And for the live shows - massive is an understatement. 1.3 million in Houston, draining the power to FBI building? 3.5 million in Moscow. And the Laser Harp.
Ray Manzerak (The Doors) for services to the organ, Bob Mayo (Peter Frampton) for services to the concept of the Live Double Album, Dave Brubeck for services to polyrhythms, Jimmy Smith for bringing the Hammond to prominence and something other than a church instrument.
[/essay]
I could go on, but this is quite long enough!