Rookie Scribe
For technical ability, I don't think anyone can beat Alvin Lee -- even Jimi Hendrix, who was more of an interesting improviser or many of the other genii mentioned in this thread. It wasn't just that he could play fast, what he played was amazing.
I'd compare him to Paganini - being a virtuoso is wonderful and important, but it's not the only quality that makes a musician; it's like mathematics: the fastest and brightest mathematicians have not contributed the most to math. Some of the greatest have been positively slow in their thinking (Norbert Weiner comes to mind)
The Wood Chopper's Ball shows off the talent I'm describing much better than his famous I'm Going Home.
This version is one of my favorites (apologies for the really poor quality on YouTube) -- and the interplay with Leo Lyons (bass) at the end is something to experience.
Thanks for considering. I'm interested in others' ideas: I'm pretty confident Alvin Lee is a great technical player; my thought is that others are less moved by this aspect of musicianship for whatever reason.
In the spirit of our website--I think it's about what really turns you on, which we all know is highly variable!!