Posted by Rachel Leigh - email

(WFLX) - Success on Idol is easy to gauge: If America likes, you survive to sing another week. But how do you measure success after Idol? Record sales? Awards? Screaming pre-teen groupies?

The biggest sign you've made it: You go by just one name, like Carrie, Kelly or Daughtry. But ask Idol heads who the best is and the resulting arguments can make Simon and Paula look like an old married couple.

"There's no better way to start an Idol fan war on the Internet than to ask who is the most successful Idol because the Carrie fans and the Kelly fans and the Daughtry fans come out with their own sets of number, like number of singles sold, number of albums sold, overall albums sold," said Michael Slezak.

So let me, your humble Insider, have at it. Nineteen million albums sold and that's before her new album dropped this month. Country crooner Carrie Underwood has banked more bucks earning $9 million last year alone. Plus, she's received the top country music award by being inducted into the Grand Ole Opry.

"Nobody ever knows what to expect when somebody wins American Idol," said Carrie Underwood. "The public can continue to support them. They are the ones who made them the American Idol."

Daughtry Idol's original rocker got the boot way too soon, but showed up everybody by topping the charts with one hit after another. Between them all, they've won him Grammys, Country Music Awards, and too many American Music Awards to count. But only one has the granddaddy of awards on her mantle.

Jennifer never left Hollywood, she embraced it and won an Oscar for her performance as Effie in "Dreamgirls".

So, what about last year's crop? "In 2008, the winner of the Google Olympics for Idol contestants was David Cook. Clearly, there are a lot of fans who want to wallpaper their desktop with pictures of him," said Slezak.

David is already lighting up the charts and little David isn't far behind.