In reply to S****** Blonde.

Actually that is Barbra Streisand.
Here is the list:
1. Barbara Streisand
2. Madonna
3. Mariah
4. Whitney
5. Celine.
The reason why people call Mariah best selling female artist of all time is because the time frame that it took her to sell that many albums. Mariah accomplished this during the 90s early 2000s what took her counterparts to do in 20 years or more.

They are all big seller, but Madonna accomplished this feat in 30 years what took Mariah 22 years....

But in all actually the biggest selling female artist of all time is actually Babara Streisand.