In reply to Goucho:
The short list:
Fred Nicole. Quietly being a genius for the past 25 years. From early hard routes like a repeat of Wall Street in 1987, to "Bain De Sang" in 1993 and "Elfe" in 1994, to Danse Des Balrogs, Raja, Dreamtime. I watched him, 3 or 4 years ago, still crushing in Hueco, and marveled at his grace, his gentle touch on the rock, and his forearms, which eclipsed the sun.
Wolfgang Gullich. Pioneer, visionary, with accomplishments from "Riders on the Storm" to "Kanal Im Rucken". World Cups and Big Walls. He seemed to be everywhere for a couple of years.
Jerry Moffatt - because he's the bloody Picasso of rock. Genius on an intuitive level. With brashness and talent like few every had - "I like burning people off."
But if, in the spirit of your question: I can only pick one - it's Jerry. The picture of him on The Dominiator, which graced an old issue of Rock and Ice, altered my understanding of what climbing could mean in terms of difficulty. Jerry was a driving force in climbing even over here in Canada, and each time a new Climbing mag arrived in the mail, there was another article on another preposterous thing that Jerry had done. I'll always remember the picture of him soloing something at Stanage with a cast on his leg after crashing his motorbike.
I can still quote most of his statements from "One Summer" and "Real Thing".
I'm a hopeless fanboi