Best Female Voices
This is easy...there are some really great musicians that people have mentioned, but they don't have great voices. An example of this is Sarah McLachan. She is a great overall musician, she can write, sing, and all that. But when you have just pure voice there are only a few great ones. These fall into two categories, pop type and folk type. In the pop category we have Mariah Carey, Whitney Houston, and that's that. In the folk category, Charlotte Church, Loreena McKennitt, Hayley Westenra, and Enya. Sarah Brightman maybe, but I haven't heard enough of her.
For all those that like Enya type...check out Hayley, she is awesome.