'American Idol' has been introducing us to stars for over a decade. Some of the winners from the reality competition, now airing its final season, have been more successful than others, but winning is not necessarily required to reach super-stardom. In fact, when looking at album sales from American Idol alumni, two of the top five did not win the seasons on which they appeared. Here are five former 'American Idol' contestants that did not win, but have still achieved massive success following their appearances on the show.

Jason Kempin, Getty Images
Chris Daughtry

Chris Daughtry appeared on the fifth season of 'American Idol.' He finished the competition in fourth place, but has since gone on to become the third-best-selling 'American Idol' contestant, in terms of album sales and single sales. Daughtry, the band that Chris fronts, has earned several Grammy nominations, and has won honors at the American Music Awards and Billboard Music Awards.

Paul Hawthorne, Getty Images
Clay Aiken

Clay Aiken was the season two runner-up. In addition to recording and touring, Aiken has appeared on numerous television shows, has performed on Broadway, and was once a 'Celebrity Apprentice' contestant. Aiken recently expressed an interest in running for office in his home state of North Carolina.

Christopher Polk, Getty Images
Kellie Pickler

Kellie Pickler has released several hit country songs since finishing sixth on season five. Her debut album has been certified Gold, and she has taken home three CMT Music Awards. Pickler and partner Derek Hough won the sixteenth season of 'Dancing With the Stars.' Kellie famously shaved her head to show support for a friend who was battling breast cancer.

Valerie Macon, Getty Images
Jennifer Hudson

Third season contestant Jennifer Hudson has gone from 'American Idol' contestant to Academy Award winning actress for her film debut, 'Dream Girls.' The performance also earned Hudson a Golden Globe Award, a BAFTA Award, an NAACP Image Award and a Screen Actors Guild Award. Her debut album took home a Grammy and has sold over a million copies. She has performed at the White House and the Super Bowl. Last year, Jennifer Hudson earned a star on the Hollywood Walk of Fame.

Christopher Polk, Getty Images
Adam Lambert

Season eight runner-up Adam Lambert released his debut album soon after his appearance on 'American Idol,' and went on a world tour. The following year, he received his first Grammy nomination. Lambert began performing with legendary rock band Queen to honor the group's late frontman, Freddie Mercury. Lambert recently joined the cast of the hit Fox television series 'Glee.'