She’s been mentioned before, but it bears reemphasis: Ella Fitzgerald! Arguably the greatest vocalist of any gender or style of music in the history of recording.
In the realm of the living, Kate Bush is a great vocalist.
And do not miss Ute Lemper. Try this:
Very honorable mention to DeeDee Bridgewater.
In the classical realm, there are many great female singers. Maria Callas. Joan Sutherland. Renata Tebaldi. Among living, active sopranos, Lise Davidsen.
Wagner wrote great stuff for the female voice. But perhaps surpassing him in this category is Giacomo Puccini.