If I had to pick just one it would probably be a 3 way tie between Santana, Hendrix or Victor Jara. Probably More towards Jara because I've been listening to his stuff more and more lately.
Chilean protest folk music from the 70's. Sort like a brown Bob Dylan that can actually sing.
Edit: In the spirit of friendship, sorry for the Dylan dig. I did just come around to Jack White though, I wouldn't use the word "genius" but I like him as a person now, so I have to hate on someone a little harder.