It's become the grand-daddy of this kind of show. However, other than Carrie Underwood, the winners haven't had the kind of careers one might hope for, given the hyper-attention they received for a few months. But I guess that's par for the course in artist development. Once the show's over, they move on to the next big thing, and the previous year's winner is forgotten.
Replacing Simon will be tough. Unlike the other judges, Simon wasn't an artist, but a label person. That's what's missing from the panel now. Someone who can think about making a commercial superstar and not just picking the best or most popular karaoke singer. Then again, that kind of person seems to be missing from the music industry. Which may be why they're having so much trouble finding someone. They can promote the flavor of the month, but no one's building long term careers.