Getting to see and hear Cotton and other old Bluesmen in the Bay Area (thank you Bill Graham) beginning in 1967---the "Blues Revival" brought on by the 60's British Bands and the Americans Paul Butterfield, Charlie Musselwhite, and a couple of others, it put the playing and singing of the young, white, imitators in proper perspective. Not to be a snob, but there was no comparison.
Blues is more than a musical style---it is the result of a lifetime of living. You can't "learn" that, you have to earn it. Interestingly, the original Fillmore Auditorium was named after the San Francisco district in which it was located, a lower-income black neighborhood. Yet the audience for those early Fillmore Blues-themed shows was 100% white, the Bluesmen playing for white Americans for the first time in their lives. To their credit, the honorable white performers acknowledged the Blues originators, the inspiration for their own playing and singing.