I was putting up a poll, but I took to long filling in the fields and it cut me off.
I was thinking Hendrix, B.B. King, Santana, John Bonham and John Paul Jones, George Harrison, and Clapton. I think these guys contributed the most to public recognition of guitar playing and music as a whole, and inspired legions of music fans to actually pick up instruments.
I feel the same way about Joe Satriani, he is a great player, but his music does not reach me in any way. I can appreciate the skill, but I can't listen to for long, I get bored. Music gotta have soul!
Oh and Malmsteen is so ovverated.. Sure he is good at the thing he does.. but he only does that one thing.. If you watch the DVD of the big 3 in concert (or were lucky enough to go see it) then you would have been embarrassed for him having to compete with Vai and Satriani
Clapton in cream is a good one.. Its difficult to distinguish influential from pioneering and technically skilled. My personal guitar heroes (and i suggest you check out all their stuff)
Rock - John Petrucci, Steve Howe, Eddie Van Halen, Steve Vai, Joe Satriani (honorable mention to the Yngwie)
Metal - Randy Rhodes, Toni Iommi, Zakk Wylde
Classical - Al De Meola, Rodrigo y Gabriela, John Williams
If you are a fan of the blues, and music in general, you owe it to your self to go out and buy Riding with the King, by B.B. King and Eric Clapton. It is a great collaboration. Also Me and Mr. Johnson by Clapton is amazing. A great collection of legendary blues man Robert Johnson covered with a great amount of heart and respect.