I love this song actually. It definitely would have gone #1 if they had made it an album only track and later released it to itunes as a single when it was released to radio. It still did pretty well though. huge WW.
Gaga has six 3m seller:
Just Dance
Poker Face
Paparazzi
Bad Romance
Telephone
Born This Way
Katy has 6 also:
I Kissed a Girl
Hot N Cold
California Gurls
Teenage Dream
Firework
E.T.
Katy is more likely to take the lead again once Last Friday Night reaches 3m.
Gaga has no song that is close. the closest is LoveGame which is around 2.5m only. Alejandro 2.2m.