1. Kelly Clarkson, winner, season 1
Clarkson, 33, recently returned to Idol in its final season and had the audience in tears with an emotional performance of her latest single, Piece by Piece. It's a fitting bookend, as Clarkson had the same effect when she belted out her coronation song and first single, A Moment Like This on the finale in 2002. Clarkson's powerhouse voice and dynamic presence signalled the music industry should take these reality show contestants seriously. Her first two albums, Thankful and Breakaway sold about 10 million copies, and her pop tunes became empowerment anthems across the globe.
2. Carrie Underwood, winner, season 4
The country music landscape for women is bleak right now, save for two female superstars: Miranda Lambert and Underwood, now 33. The Oklahoma native arrived for her Idol audition in 2004 as a 21-year-old college student with every intention of going on to a "practical" job. Then she blew the judges away with her rendition of Bonnie Raitt's I Can't Make You Love Me and sailed through to the finals. Her first album, Some Hearts went seven-times platinum and she has co-written about half of her 23 No1 hits since.
3. Adam Lambert, second place, season 8
Lambert's soaring falsetto made him an instant front-runner, especially when his performance of Mad World drew a rare standing ovation from the always-prickly Simon Cowell. The Freddie Mercury comparisons started early and, by 2011, he was performing with Queen, eventually standing in for Mercury as the band's lead singer. Lambert, 34, raked in enough cash last year to land the No1 spot on the Forbes list of Five Highest-Paid American Idols In 2015, earning about $10 million.
4. Chris Daughtry, fourth place, season 5
Cowell was initially dismissive of Daughtry when he sang a gruff version of Joe Cocker's The Letter at his audition. Cowell said no, but Randy Jackson's and Paula Abdul's votes put Daughtry through to Hollywood. Daughtry went on to prove rock artists could thrive commercially after the competition. After he was voted off, Daughtry, 36, started an eponymous band whose music became a mainstay on Top 40 radio. Though the band slowed in later years, the Daughtry self-titled debut album was a smash, spawning five hit songs.
5. Fantasia Barrino, winner, season 3
Barrino's haunting, powerful rendition of Summertime in 2004 is often cited as the best performance in Idol history. Her coronation song, I Believe flew to the top of the charts after the finale. Later, Barrino, 31, released four albums, appeared on Broadway in The Color Purple and After Midnight and won a Grammy Award in 2011 for Bittersweet.
6. Mandisa, ninth place, season 5
Several Idol artists went the Christian music route (Danny Gokey, Chris Sligh, Phil Stacey), but Mandisa flourished the most with five albums. Cowell was quite nasty to her, making a crack about her weight and asked if there was a "bigger stage" for that season. Mandisa, who has lost more than 45kg since 2006, made headlines when she forgave him: "If Jesus could die so that all of my wrongs could be forgiven, I can certainly extend that same grace to you." She has been nominated for four Grammys and won Best Contemporary Christian Music Album in 2014 for Overcomer.
7. Phillip Phillips, winner, season 11
Would you believe the top-selling song from any contestant in Idol history is Home? Apparently, "Ahh-ahh-ahhs" and "Ohh-ohh-oohs" and gentle guitar-strums were what people craved. It sold 5 million copies. Phillips, 25, reminded the world that after years of falling ratings, Idol still existed and could still lead to success.
8. Josh Gracin, fourth place, season 2
Idol made strides in pop with Clarkson's win, but was insular, traditional Nashville going to accept a country singer from (gasp!) a reality show? Gracin's breakthrough was a resounding "yes". His first single, I Want to Live, was a Top 5 hit and helped to propel his self-titled debut record up the charts.
9. Jennifer Hudson, seventh place, season 3
Hudson is known as Idol's most triumphant story. She went from seventh place finisher to Oscar winner. Dreamgirls and And I Am Telling You I'm Not Going made the biggest impact, but she also had several R&B hits and kept the momentum going with her third record, JHUD, in 2014. Her first album, Jennifer Hudson, resulted in three Grammy nominations.
10. Kellie Pickler, sixth place, season 5
Back in 2006, the quirky North Carolina native charmed everyone with her naivete and cluelessness about calamari. After she was sent packing, Pickler landed a record deal that resulted in a gold-certified record, Small Town Girl. She's not as dominant as her Idol country counterparts, but Pickler, 29, has remained a critical favourite - and a boost to the genre's credibility.
