Oh my god at Lady Gaga getting so many votes. SMH.
Mariah Carey's voice has died down drastically and is nothing what it used to be. She always pulled the same trick anyway: high note at the end of a song.
Beyoncé has improved whitin each era and she can dance her ass off while hitting perfect falsetto notes.
P!nk is extremely underrated.
That said:
Beyoncé > P!nk > Mariah > Christina > The rest.