Madonna has never impressed me as an singing artist. Instead, her popularity seems mostly tied to her ability to create a controversial personae, then, when it beomes stale, reinvent it. She literally beomes someone "new" with each album. This, of course, appeals to her chosen audience which is both the demographic that spends the most on records and the one with the shortest attention span. Thus her visibility remains high, and in turn her record sales, but it has little to do with artistic skills.
In other words, great marketing, fairly mediocre musical skills.
In other words, great marketing, fairly mediocre musical skills.