I don't play guitar so I'd feel like a fraud rating the skills of someone who does. It's like "best brain surgeon". How the hell would I know?
Nonetheless, I do have favorites. Not saying their, there, they're (just being safe) the best but I like:
Robert Fripp
Billy Zoom (the nicest man in punk rock)
This kid ---->
http://www.youtube.com/watch?v=QjA5faZF1A8&eurl=