Christina appears 4 times:
With long, crimped extensions and a bouquet of roses covering her up, the nude singer graced the cover of W magazine's "Music & Style" issue in 2011.
While pregnant with son Max, the singer proudly showed off her baby bump for Marie Claire in 2007.
Aguilera appeared nude on the cover of Maxim in 2003.
A year earlier, Aguilera appeared naked -- except for a guitar -- on the cover of Rolling Stone.
Rest of the list, and pics here -
http://www.billboard.com/photos/1484...pears?i=542014
