Photo: Gries/Getty

Born December 18th, 1980 Key Tracks "Genie in a Bottle," "Beautiful," "Ain't No Other Man" Influenced Danity Kane, Kelly Clarkson

"I knew she could really sing," Herbie Hancock said of his 2005 collaboration with teen pop's most accomplished vocalist. "But I didn't know she could sing like that. She knocked me out." Christina Aguilera has had the finesse and power of a blues queen ever since she was a child star (she appeared on Star Search at age 11). Even in her teen-pop "Genie in a Bottle" days, she was modeling her dramatic, melismatic technique on old-school soul heroines like Etta James; you could hear it first come to fruition on 2002's "Beautiful." Patti Smith, of all people, says Aguilera's rendition of James Brown's "It's a Man's Man's Man's World" at last year's Grammys was "one of the best performances that I've ever seen...I sat and watched it, and at the end, I just involuntarily leapt to my feet. It was amazing."

1. Genie in a Bottle
2. Beautiful
3. Ain' No Other Man
4. Keeps Gettin' Better
5. Candyman
6. Hurt
7. Fighter
8. What a Girl Wants
9. Lady Marmalade
10. I Turn to You

• View List: The 100 Greatest Singers of All Time
• Listen: The Ultimate Singers Playlist
• The Ballots: View Handwritten Votes
• Legends at Work: In the Studio Photos
• Voters & Methodology