My personal top 5:
1) Jimi Hendrix - no one man has so embodied the spirit and vitality of the instrument as much as him, and no one ever will
2) Jimmy Page- the greatest riff-write ever, coupled with a down-hone blues style that effortlessly merged with a progressive mentality to create an entirely unique musical sensibility
3) Eric Clapton - not even Jimmy Page has managed to fuse rough, down-and-out blues with accessible pop music as well as Clapton. It also helps that Clapton is one damn fine player
4) Duane Allman - The greatest white American blues player, bar none. He died as he climbing the mountain; who knows how good he could have been if he had lived to reach the top
5) Jeff Beck - Despite his lack of popularity compared to his other Yardbird alums (Clapton, Page), Beck has managed to create a playing style so smooth, with such a beautiful melding of jazz, blues, rock, and even techno, that he in many ways surpasses them