These aren't exactly metal guitarists, but all are great.
(1) Jimi Hendrix- still the best ever!
(2) Mark Knopfler- best finger picker
(3) Eric Clapton- king of the blues, plus he's played with almost everyone else on this list
(4) Stevie Ray Vaughn- Hendrix reborn, almost
(5) Richard Thompson- great finger picker with a Celtic background
(6) Carlos Santana- brought Latin overtones to rock, improved with age
(7) Eddie Van Halen- brought "tapping" technique to rock
(8) Jimmy Page- heavy blues, the father of all metal guitarists
(9) Bonnie Raitt- best slide player
(10T) Jeff Healy- self taught blind guitarist, with a playing style like no other
(10T) Billy Gibbons- Texas blues, Hendrix's favorite guitarist