My favorite guitarist are ( for their technical prowess and/or compositions ) :
-Luca Turilli
-Micheal Romeo
-Alexi Laiho
-Micheal Weikath
I didn't listen a lot to the following guitarist but they sure impressed me :
-Paul Gilbert
-John Petrucci
-Micheal Angelo Batio ( check out his quad guitar video on youtube, real or not?)
-John5
-Steve Vai
See ya!