FlyBoi, Music Of The Sun did 2 million worldwide, A Girl Like Me did 4.5 million. Chris Brown and Exclusive both did 3 million a piece worldwide. Their first two albums sold roughly the same amount (minus 500,000 copies), however with their third studio albums, Rihanna clearly came out on top. It really has nothing to do with who has more albums as she only has one more over him. And even if Rihanna stopped at the third album, she's still have him beat.

Or better yet, let's pretend GGGB doesn't exist and that Rated R is her third album. She'd still have more in sales as Rated R, while not doing anywhere near the numbers it should have, has most definitely surpassed Graffiti significantly.