I am surprised that nobody has mentioned Tommy Tedesco, the great studio guitarist, who made his living by being versatile. I would guess that he played every style at one time or another, for and with the best. And he kept it up for years. He was a great site reader, as well.

There is a difference between being a versatile player and being a great artist, and on that note, I'd have to say that I vote for Bola Sete, who was an incredible Bossa Guitarist, and who was also regarded as a classical guitarist in the rank of Segovia.

There is another area, and that is the area of theory--because, bottom line, in order to play in different styles you have to understand the fundamental musical ideas that are the basis of each style, and how to use them.

Love him or hate him, Dennis Sandoli, who seldom performs, but has taught for many years in Philadelphia, is the master in this area. People like Pat Methany have studied with him, as have Art Farmer and John Coltrane. Sandoli's guitar students are like a a music Mafia in Philadelphia. playing everywhere in everything from the rawest of thrash bands to TSOP style R&B, to all types of Jazz. Sandoli has a rare talent for taking the genre, breaking it down, and putting it back together in a way that you can build on.

(And no, I never studied with him, don't necessarily recommend it, and am not necessarily even an admirer--but that is another discussion)