Justin Bieber
Tireless touring and tweeting with his 36 million Beliebers helped "Believe: Acoustic" hit the top in 2013, making Bieber the first artist ever to have five No. 1s on the Billboard 200 before age 19.
Taylor Swift
The masses connected with Taylor's emotional songwriting and embrace of many genres on 2012's "Red," allowing her to become the only woman to have had two albums sell 1 million copies in a week.
Bruno Mars
With his "Unorthodox" mix of classic soul and modern pop, Mars eclipsed the competition and scored his first four Hot 100 No. 1s, including "Locked Out of Heaven," faster than any male artist in almost 50 years.

