I'd have to say Madonna, Britney & Mariah Carey

All 3 have influenced an entire generation of artists!!!!

I agree

Madonna, Whitney and Mariah.

I would put Whitney instead of Mariah but out of that you're right.

Whitney, Madonna and Britney.

Madonna, Whitney Houston, and Rihanna. Three legends.

Madonna, Britney and Whitney.

Madonna, Whitney, Britney. Depending on how Gaga's next few album cycles go, I could see her overthrowing Britney easily.

Britney
Lindsay Lohan
Paris Hilton

Madonna, Britney, Whitney, Mariah, Janet. Can't pick 3.

Madonna, Britney and Diana Ross/Aretha Franklin

Madonna, Whitney, Britney

Gaga doesn't even have her oops I did it again yet. Should I mention baby one more time?

If we're not going way back to the Barbra, Cher, Tina days... then Madonna, Mariah and Janet by far. Not people seriously mentioning Britney

Mariah is more influential when it comes to vocals and music trends

Madonna
Whitney
Mariah

Like of all time? Madonna, Whitney, and Mariah.

Are you talking about hits or album sales? If its album sales, that's irrelevant because literally no one in the world is going to be selling 30 million albums any time in the distant future. Gaga has eclipsed Britney in every department (singles, tours, acclaim, awards, etc) but album sales and cultural impact (she's not far off).

Madonna
Whitney
Janet

Madonna, Whitney, Mariah/Janet.

Not even a fan of Mariah/Janet but it's so obvious.