It's all opinion, but here's mine anyway hehe
Hendrix, Vaughn, Clapton, Van Halen etc... are in a completely different league than Vai, Malmsteen, Satch, Gilbert, etc... which are also in a whole other league than say Page, Lennon, Richards, Iommi, etc...
The difference to me between the groups is this:
Hendrix and all those players were very innovative for their time, they played the instrument in ways and directions that influenced changes in the very culture of their times not to mention countless imiatators and fans.
Page and that group to me seemed to owe, at least in part, to being the right fit in the right band at the right time. The "whole is greater than the sum of it's parts" idea. I'm not saying that the bands carried these great players, just that it seems like without the band as a whole around them they accomplished far less.
Then the Vai group to me are the musician's musicians. They are (arguably) advancing the boundaries of guitar playing every bit as much as the first group, but they are having nowhere near the cultural or musical impact of those before them. They are flying below the mainstream radar for the most part, and their music doesn't cross that boundary between the student and the average person so to speak. It usually seems to go over the head of most people.