This is how I'd rank it:

Elvis Presley
The Beatles
Michael Jackson
Madonna
Bon Jovi
Britney Spears
Beyonce/Destiny's Child
New Kids on the Block
Justin Timberlake/*nsync
Janet Jackson
Backstreet Boys
Christina Aguilera
Usher
Gwen Stefani/No Doubt
P!nk
Lady GaGa
Rihanna
Kylie Minogue
Fergie/Black Eyed Peas
Katy Perry
Ke$ha
Kelly Clarkson

Avril, of course.

1 of us counts like 50 of the others

Just like 1 of you counted for 50 views of "Girlfriend" per minute on YouTube?

You know how we roll

8x times platinum US
10x platinum in Canada