I come from a generation after the previous posters, so perhaps predictably, I have a different take on blues. For me, who heard my first blues music from white artists, I found blues singers or players "authentic" if I felt they really meant it. Neither Peter Green's "Man of the World" nor Chritine Perfect's (as she was then) "I'd Rather Go Blind" sounded any less authentic to me than either Etta James singing the original "I'd Rather Be a Blind Girl" or say Elmore James "Sho Nuff I Do". They all had conviction and technique to carry it and they all moved me. This is, of course, completely subjective, but I see no reason why the subsequent versions of the blues should be perceived as being any less authentic than the first. No disrespect to Richard and Will, of course.