Hard to say "One" best player in the world.
I follow all kinds of music, but really only have a valid opinion on hard rock players. And it comes down to two things. Can they play just about anything? And more importantly, can they write just about anything. As Lukather often states. "Anyone can play it, very few can write it".
So with that in mind. In my opinion, Nuno is the best hard rock player alive. And may be the second best hard rock player ever. (that VH guy was pretty good.lol)
Paul Gilbert got a good mention earlier, and I kind of agree. If he can think of it in his head, he can play it. Literally, anything. But he lacks the creative writing of a Nuno, or even Mick Mars. Great players, who can write.