Who are the greatest singers of all time, male and female? Why?!

Who are the greatest singers of all time, male and female? Why?

My votes would probably go for Sam Cooke and Billie Holiday, respectively, but those are just my preferences. Let me know how you feel.

5 days ago
Kabum, that's true and I'm not trying to make any declaration. I just wanted to see what people think.

Björk - she has such an amazingly unusual and beautiful voice. There's nobody else in the world like her. She's genius! http://www.youtube.com/watch?v=dvvr4700d...

Bono from U2 - big powerful voice, so warm, so passionate. I love him. :-) http://www.youtube.com/watch?v=r8pnlhs7g...