Lambert may have lost out on the title to Kris Allen in Season 8, but he snagged the cover of Rolling Stone and continues to generate more buzz and album sales.
His censored performance at the American Music Awards last year was widely talked about. But the controversy only seemed to help Lambert sell more records.
His first album reached No. 3 on Billboard's 100 and racked up 2.6 million downloads, easily making Lambert a millionaire. His Glam Nation tour was hugely successful, with more than 100 shows in North America, Asia, Australia and Europe.
Aiken continues to surprise, ever since his second-place finish to Season 2 winner Ruben Studdard.
Since the release of his first single, Aiken has outsold and outshined Studdard, earning an estimated $2.2 million in 2009, according to Forbes.
His "Claymates" made him a hit in Broadway's "Spamalot." And when he announced he was gay and becoming a father, he made the cover of People.
Hudson didn't get past seventh place in Season 3, but in other ways she has eclipsed winner Barrino. After winning the Oscar for "Dreamgirls," Hudson starred in the films "Sex and the City" and "The Secret Life of Bees."
Her film "Winnie," in which she plays Winnie Mandela, the wife of South Africa's Nelson Mandela, is scheduled for release this year.
Her recording career hasn't done so bad either, although her first self-titled album came out in the midst of personal tragedy; a short time after it was released, her mother, sister and nephew were murdered in Chicago. The album sold a respectable 800,000 copies and earned her a Grammy.
Hudson has also scored lucrative endorsement deals with Gap, Avon and now Weight Watchers, after shrinking from size 16 to size 6.
By far, Daughtry was the biggest success to come out of Season 5. He didn't make it past fourth place, but he has easily surpassed winner Hicks.
His debut album outsold Hicks' album: 5 million to 700,000, respectively. Together, his two albums have sold 6 million copies in the United States, according to Nielsen SoundScan.
He commands stadium-size concerts and has become a fixture on radio and television
ABC News Radio's Andrea Dresdale contributed to this report.