I don't think Madonna is especially beautiful. Yes, she's had her moments, but the others mentioned so far are more naturally attractive.
Sorry I left out Liz Phair--she's gorgeous.
I liked Charlotte Church when she was still a child prodigy (and no, I'm not a dirty old man), but I've gone off her. A magazine interview with her did not put her in a very good light--well, she did not put herself in a good light.
She smokes cigarettes now! Can you imagine anything more idiotic? A successful young woman with an incredible voice actually begins smoking--not only a danger to her voice (which she apparently isn't concerned about), but her lungs, etc. She really disappointed me.
And Linda Ronstadt might have been a good choice a few hundred pounds ago.