You should've put only the ones that matter like Mariah, Celine, Whitney, Christina, Beyince, Madonna, Alicia and excluded those that don't like the rest.
I voted for Whitney on impulse. I think it was the right choice but Mariah puts up a damn good fight. It's a little tough considering both of their discographies are 75% ballads.
As for pure, consistent quality, Madonna, Alicia, Toni, Janet and Brandy are all up there for me. I love some of Bey's ballads, but I hate others.