I would say in America
Taylor Swift
Lady GaGa
Usher
Rihanna
Beyonce
but then we have...(also)
Eminem
Britt
Justin Bieber
They flip flop back and forth, especially when they have new albums out. Far as the most popluar when it comes to albums then:
Taylor Swfit
Eminem
Lady Gaga
Beyonce
Justin Beiber
When it comes to digital sales
Rihanna
Lady Gaga
Black Eyed Peas
Usher
Taio Cruz?