Just some comments of my own. I don’t think Prince is underestimated, unless someone has totally forgotten to check out his playing ever. Seeing him live doing all the guitar work is even more awesome — if he ever plays nights and especially the ad hoc jam sessions in Las Vegas I will take a night flight there.
While John Mayer, hmm, what could I say. That guy went to the crossroads and sold his soul to the marketing department, that’s for sure.
I hope the realization will sink in for the majority of consumers that guitar playing is more than trying to play as many notes as possible in the shortest time period. It takes a lot of guts to develop a personal style. I could hear immediately if for example Steve Hillage is playing.