The way you put Rihanna on Flo Rida and Pitbull's levels
She has sold over 30 million albums for ****'s sake. Her latest album has every reason not to sell, from lack of commercial appeal to messy release and marketing to streaming-dominated industry sales, and it's passing 1 million in pure worldwide sales soon and having great consistency with continuous hit singles.
Not to mention, Rihanna rules everyone in the singles department.
What does Beyonce rule everyone at? Both Adele and Taylor destroyed her at albums (and singles), Taylor destroyed her at touring and everything else, she's not passing the album sales of Britney Spears (who debuted at the same time) anytime soon.