I am more interested in artists who did not get their fame via a TV reality show/contest. But artists who gained popularity based on one TV appearance. Like how Future Islands fame came from one performance on Letterman, as opposed to Boyle (or Kelly Clarkson) who had their fame come from multiple TV appearances on a contest show. I think there is a difference. There have been tons of "famous" people to come out of the American Idol era.
That's fair and makes sense.
I still think, however, that this is apt.
Ricky Martin basically introduced himself to the world on the 1999 Grammy's doing "Cup of Life. He was well-known in the Latin countries, but he was immediately famous around the world after that.
https://www.youtube.com/watch?v=r6kkHwTWDEEEven though Ricky did already have a measure of fame, it exploded exponentially after this one appearance. I'd argue that while Future Islands did achieve a lot of buzz from that performance, it's still relatively modest.