With the ability to effortlessly play over changes, his incredible triadic approach to improvisation and the way his supreme technical ability always remains subserviant to the music:
Larry Carlton (live or as a session musician)
For having a spiritual idea of what the guitar can offer that conceptually goes way beyond what anyone else has ever done and the ability to exquisitely implement that concept:
Steve Howe (with classic period Yes)
Many, many, many other players have reached amazing levels in whatever their specialties are, but these 2 guys, at their best, have some of the broadest, freshest and most intense musical concepts and approaches ever. Songs that they are involved with become so much more than they otherwise would have been. They affect the players and composers around them profoundly.