[gtrdr]

I think the boys have more good singers across the board, whereas the best girls demolish the best boys - though the comment of pretty girls with shitty voices contributes to the former. Here are the great females that come to mind: Aretha, Ella, Janis, Billie, Sarah Vaughn, Nina Simone, Francine Reed, Tina Turner, Mariah Carey (can I change it to Black women - Janis is the only white chick on my list...).
For the guys: Robert Plant (if he really is male), Otis Redding, Marvin Gaye, Al Green, Mel Torme, Johnny Hartman, Ray Charles, Nat Cole, Sinatra, John Fogerty (maybe), Sam Cooke, Frankie Valli, James Brown, Elvis Presley, Elvis Costello, Paul McCartney.
The sheer beauty and expressiveness of the best female singers I think beats the men - only Charles, Gaye, and Cooke compare to any of the 9 ladies I mentioned (maybe Billie misses, so 8), I think the average of the women would still beat that of the three men. BUT, notice that 16 men and only 9 women made the lists, so what the fuck does that mean?

I think a good somewhat random sample would be American Idol finalists - I would guess from a fuzzy memory that the best girls are in fact generally better than the best boys, but there are still some really good male voices on that show (actually, I only would consider about 4 to 5 contestants per season to have truly good voices, so I'm not endorsing the show as showcasing good voices exclusively, which may even make it a better/wider-reaching sample of the sexes).

EDIT: I may have to add Ray Lamontagne onto my list of men - that dude's voice is simply incredible! Anyone else have opinions on that?