Jimi Hendrix
5
There is no one, single "best guitar player of all time", but Jimi Hendrix certainly belongs listed with those less famous others who should also be at the top, like Hubert Sumlin (for his magnificent work with Howlin' Wolf, who by the way was no slouch on guitar himself), Muddy Waters, Elmore James, Lightning Hopkins, John Hurt, John Fahey and Leo Kottke, just to name a few off the top of my head.
Naturally, with everyone allowed to participate regardless of qualifications or lack thereof, this list is really nothing but a popularity contest. If it wasn't, Jeff Beck would be way higher on the list than his fellow Yardbirds, Page and Clapton.
UPDATE:
How can anyone give Andres Segovia less than five stars?