best what?
Composer on the guitar?
Best tehnique guitarist?
Guitarist with biggest balls of them all?
It is very hard to say one guy is the best.....
If you go for composing and getting the best out of the sound of the guitar without any particular tehnique, you have to go for someone like Edge of U2....
If you go for tehnique, the choice is wide open. My vote would go to Stevie Vai/Satriani but thats just my taste
If you look for a guy with balls, also, there is lot of choice: Gary Moore, Angus Young, Jeff Heleay.......
And there should be a separate category for guys like McLaughlin & Dimeola. They are in may respects a category on it's own....