I am aware of the viewership, but what "Idol" has actually had any kind of sustainable success after the show?

Kelly Clarkson is the only one that comes to mind. Clay Aiken maybe, but he didn't even win, he was the runner-up. Ruben Studdard has had moderate success, but nothing like the popularity he had immediately after the show.

I could probably stand to watch AI if it actually meant something. It's just a bunch of people that can sing fighting for 15 minutes of fame.