Welcome to the forum Mozzy.
Hard to say. There's guys like Segovia and other guys like Andy McKee and then still other guys like Eric Clapton. How do you compare Segovia to Clapton? Each are incredible in their own style, and arguments can be made that each is the best living player in their style. Yet arguments can be made that there are others who are better. Then you take Leo Kottke who created his own playing style, and then think of Andy McKee who improved on it. Which of those two is better? Each is amazing, and each is innovative. But who's better? I don't know.
All that said, I think everyone can agree that Stevie Ray Vaughan deserves mention. Put all that other stuff aside, and he's just awesome. Watching his hands while he plays, it's just effortless. I can't even keep up with what he's doing, but it's completely effortless looking. Same for Doc Watson. I don't know if you like country folk music, but even if you don't, pull up a chair and nice cup of whatever you like to sip upon (some peppermint tea with honey would be good) and watch some Doc Watson videos on Youtube. The man is faster than lightning. He'll rip out 40 notes and you won't even see his hands move. Malmsteen has nothing on him for speed.
Speaking of musicians who can play across styles and are innovative, you have to mention Malmsteen. He may be the epitome of it - someone who has taken Classical stylings and turned them into heavy metal is one heck of an innovator.
But don't forget Roy Clark. He can play the back of a guitar better than most people can play the front. Forget about the Hee Haw schtick. Roy Clark is one amazing musician. Bear in mind that he earns his money from country, but his main musical love is jazz. What he plays on stage isn't even his best work! Oh, I'm sure he loves doing it and puts his heart into it and I mean no disrespect, but his main love is jazz.
I guess my point is that it's hard to say "best." But I think we can all agree, they're all better than me. Though there are surely some mutants on Chordie who can give some of these guys a run for the money. Or the glory, because Chordie doesn't pay.
- Zurf