I think Bill really misses a big point comparing Madonna to Elvis. They were both cultural icons whose primary appeal was that of performer, not really great "artists." Elvis really did break some new cultural ground though, unlike Madonna. As a cute white boy, he could could channel a good bit of scary sexual rock n' roll excitement to a white audience in a way that black artists couldn't at the time. I don't hold that against him though, he was a product of the times just like we all are. Before Tom Parker got a hold of his career, he really did have lightning in a bottle for a brief period. It's easy to forget the first Sun recordings in light of the long Parker/RCA period that followed.
