Julian Bream. The greatest guitarist ever, without a doubt. Segovia and John Williams are a close second and third. They are beyond anything, of another other style included.
Mainstream..
Acoustic…
Nick Drake and Elliott Smith. Kind of similare but amazing chord structures and finger picking.
Plugged in…
Steve Jones from the Sex Pistols. Unbelievable guitarist. Wrote some amazing riffs and had to put up with all the punk stuff.
Hendrix. By far the best electric guitarist. Not technically, but he was born with nothing, was black, which at the time was a bad thing in that part of America, came to London, blew every other musicians mind and became worldwide name and a legend forever, and it was all down to his playing and creativity.
Cobain, was good as well, to front a band like that, singing and churning out that music night after night, takes some doing.
I don’t know, there are so many. All imo, obviously. 🙂