I think Madonna and Robbie probably.

my list...I think this is right :unsure: its in the order of who we think has sold more right? :unsure:

 

1998-2006

 

1| Ayumi Hamasaki 55 million +

2| Destiny's Child 50 million

3| Madonna 40 million

4| Shakira 35 million + Singles

5| Utada Hikaru 33 Million