1. Aretha Franklin is not the biggest Blsck female artist in history in terms of success(maybe in term of critical acclaim) . Whitney Houston sold 45 million copies of one album and she's at about 200 million overall. You ask a random person in every part of the globe who Aretha Franklin is and who Whitney Houston, Beyonce, and Rihanna are and you're not going to get near the same amount of responses. If we're talking women from her generation, Diana and Tina are bigger. Having the most charted singles isn't that big of deal, she's had a very extensive career and released a lot of content. Dionne Warwick has the second highest number of charged singles, you're not going to try to argue she's the second most successful Black female artist.
2. I have no idea who Ruth Brown is. They're not talking about this one even when Gladys, Aretha, Patti, Ella, Sarah, etc. are getting mentioned so she can't be that big. Her Wikipedia page indicts she was popular in R&B but you really think someone in Taiwan, India, or even Canada knows who she is? It was even mentioned in the news when she died. Popular in the Black community does not equal international superstar.
3. I'll take your word for it
None of these three women are Pop Stars are sexual desirable so my point still stands.
4. Brandy's success was decent but short lived. She doesn't even have a #1 album. Destiny's child is basically Beyoncé and background singers.