Well, those kinds of rankings are typically based on popularity as much as anything. I have no idea how one would rank 'best guitarists' since it's impossible to be objective about it. What impressed me about Prince wasn't his technical skills [at his level they're all pretty much off the charts, technically] so much as his ability to move around the stage without messing up a riff lol.
Now, if you break it down into categories it's a little easier: best rock/pop, best blues, jazz etc. Or maybe best innovator in each category. Hendrix was probably the best blues/rock innovator. As a hobbyist I can watch Clapton or Stevie Ray and see what they're doing---might not be able to get the same sound lol, but it makes sense from a technical aspect. Hendrix was different. It was more like organized chaos. Hendrix was doing things back in the 60's [!] that were pretty crazy by even today's standards.
Go back father before the advent of the electric guitar, Django Reinhardt was doing things that people still try to mimic many decades later. Both of their influences are everywhere.
Or you could go with best slide guitar innovator and Duane Allman wins that hands down. It's fun trying to rank them but I don't know that it really means anything since the guitar is an instrument that can produce such a broad range of sounds and music.
