http://www.youredm.com/2014/04/10/generation-sex-whos-mainstream-artist/
The company took anonymous information from 35 million songs and over four hundred apps to procure the answer to the question I asked in the title. The most mainstream artist, who is loved by the widest audience, at least right now, is Bruno Mars.
Daft Punk was also the second most popular act for males, being topped by the one and only Eminem.
Eminem is the #16 mainstream artist amongst women.