In reply to ThatBoyLuke.

Sorry but Gaga has already sold a similar amount of ALBUMS as Rihanna and Beyonce, but in just 4 years
About the others... Xyina never was as big as Gaga has been this last 4 years (kkep in mind albums sales are not what they were in 2000 when Xtina sold more)
And Britney would be the only one with massive album sales. But her career and little talent ended really quick, while Gaga has the talent to perdure, that´s why I´m positioning her above Britney, I´m anticipating the inevitable