Mariah Carey's Merry Christmas (15million copies sold worldwide)

She has sold nearly 50 million albums worldwide, making her one of the best-selling artists of all time.

Britney Spear's best selling CD was her first album, ...Baby One More Time, which sold over 26,000,000 albums worldwide.

I think the best selling album at the moment is either Adele's Album 21 or Michael Buble's Christmas

Here is a list of some best sellers i found on the web.

http://bestalbumdeals.com/greatest-albums/the-best-selling-albums-of-the-year-2011

Bodyguard sold 45 million copies worldwide and is the 4th best selling album worldwide, i will always love you sold 12 million.