Obviously Idol doesn't do its job well, if you consider its job to be pumping out stars. Given months of top quality TV time, sizable fan bases, and grade A studio and marketing assistance, only Kelly Clarkson and Carrie Underwood have really done anything. Taylor Hicks could be dead and nobody would know. David Cook is rapidly becoming irrelevant. Reuben Studdard is dead and nobody cares. Fantasia is on Broadway, which I guess is a form of success. Jordin Sparks sings the National Anthem at sporting events, which is not a form of success.
I think it would be interesting to look at modern pop stars through the American Idol framework -- i.e., how would Justin Timberlake fare on Idol? I specify "interesting" and not "useful" because the AI platform is quite dissimilar from the real world conditions that music biz hopefuls face. Let's take Timberlake to illustrate. Now, we're talking a bare bones Timberlake, stripped bare of his celebrity, fame, and N*Sync history. Timberlake is immensely popular because he is attractive; he knows how to dance; he has the benefit of working with Timbaland on most of his songs; he has a great public persona and degree of charm about him; and he straddles several genres of music, thus making him appeal to a large variety of music fanbases. Now -- what aspects of this would be useful on Idol, where unknown quantity Justin Timberlake has to sing Sam Cooke one week and Big Band the next and "Roxanne" after that? It would generally be disingenuous to say Idol is a singing competition, but when you take Idol vis-a-vis a career based around dancing, marketing, and songwriting -- Idol's a singing competition.
Let's take a look at the top 4 finalists from the last 3 American Idols for further clarity on what I'm getting at:
Season 5
Taylor Hicks: People considered him soulful. He did a lot of horrible dancing, and was very energetic. Markedly older than the other contestants. Had no appeal then, has less now.
Katherine McPhee: Very pretty and had a great voice. Fairly old-fashioned though, as evidenced by her constantly singing "Somewhere Over The Rainbow."
Elliott Yamin: Quirky little Jew, not very appealing. Not a good singer. R&B by white artists really isn't in these days.
Chris Daughtry: Obviously very big as far as Idol contestants go, with Fuel and then with Daughtry. Big voice, ripe for top 40 conventional modern rock.
Season 6
Jordin Sparks: Pretty, not great looking. Good singer, but again -- there is no real market for a Whitney Houston cover singer.
Blake Lewis: Weak singer, very current, very creative by Idol standards. Lots of beat-boxing type stuff. Slid through on charisma, good looks, and creativity.
Melinda Doolittle: Bombastic voice, absolutely hideous face and body. Second most unmarketable creature ever.
LaKisha Jones: She gets the honor of first. Not even worth discussing. She could be a back-up singer in a "Lady Marmalade"-centered bar band or something.
Season 7
David Cook: Big, deep, screamy voice. Rode in on hipness, creativity, and vocal skill.
David Archuleta: Technically a good singer. Girls found him adorable. Ultimately fairly robotic and lifeless.
Syesha Mercado: Black, not-good-but-pleasant voice, good-looking, and current.
Jason Castro: Complete joke, stoner Jesus freak. Another not worth discussing.
Finalists, it seems, excluding fluke feel-good stories, are usually good singers in the karaoke American Idol sense of the term "good singer." However, this quality is not at all predictive of real world Billboard/MTV success. Jason Mraz, Miley Cyrus, Katy Perry, Pink, Amy Winehouse, Usher... how would these people fair on Idol? Not well. The producers make contestants sing modern pop, 90s rock, power ballads, Motown, Michael Jackson, Whitney, Tony Bennett, 80s synth, The Beatles -- why? For entertainment, clearly. But it should surprise nobody that the cream of the Idol crop, those left standing at the end of the day, are most often jacks of all trades, masters of none. Can you imagine Usher trying to sing Bon Jovi?
Obviously there are some big names in music these days that would do well on Idol. (Just as -- occasionally -- there is a big name on Idol that does well in mainstream music.) But they are few and far between.
John Mayer would likely do very well. Sultry voice, girls would love him, he can sing a bunch of styles and his guitar playing would put him over the top, as actual instrument playing is the sign of godliness on Idol.
Alicia Keys would do great for many of the same reasons. Good looks, good pipes, piano playing, good range, and the right shade of skin color for Idol voters.
Rihanna would do terribly. Britney as well. Both would get far enough on pure lust votes, but in the end neither can sing and neither will have the power of songwriting on their sides.
One of those lame James Blunt or Robin Thicke types would likely be well served by the Idol format.
Nelly Furtado and Shakira -- both no.
Christina Aguilera seems like the one jump out. She would totally destroy Idol. It wouldn't even be close.
Beyonce would do well enough, I presume. But her act is performance-heavy. So while her voice is certainly good by Idol standards, I question how enrapturing she would really be on the show.