It looks like you answered your own question within your question! :-)
I can't add anything else to what you have already mentioned. Some people are just born with "it" and they know how to develop their gifts. Having said that I don't believe she has ever obtained "A" level status in the world of celebrity. By that I mean people weren't anxiously awaiting to purchase tickets to see her next block buster movie or sold out stadium concert ALA Whitney Houston (in her prime).
Nevertheless the entertainment world has always had it's share of "B" and "C" level stars who are just as talented but for some reason aren't embraced as much as other entertainers who are considered "event" entertainers who are "believed" to guarantee ticket sell outs and blockbusters once their name is attached to something.
Personally speaking I believe Vanessa Williams is a much better singer than Madonna or Janet Jackson and is much more beautiful. However it's unlikely she has sold nearly as many records or ever filled the large arenas that they did in concert.