With few exceptions, the success and failure and memorability of most competition reality shows has nothing to do with the contestants. It’s the judges, stupid. So Deadline is going to judge the judges. Criteria will include 1) Expertise in their field, 2) Confidence in their role, 3) Connecting with their contestants, and finally 4) Their charisma and controversy. We start with American Idol’s Nicki Minaj and Mariah Carey:

The gold standard of competition TV judges on American Idol is and will always be Simon Cowell. The acerbic Brit was a nobody in America when Idol debuted. But his long history as an A&R exec gave his criticisms and compliments weight and credibility. Same with Randy Jackson, who was a record producer. But short-lived Idol judge Ellen DeGeneres had no background in the music biz. A judges panel usually consist of the nice one, the tell-it-like-it-is one, and the icon or role model. A judge’s job is to rid the show of wannabes going nowhere and encourage potential stars. American Idol has three new judges on the show this season but let’s be honest: there are really only two Idol judges worth talking about — Nicki and Mariah. A sop to the country music market, freshman Keith Urban is just a pleasant prop in strategically distressed blue jeans. Veteran Jackson is just an ineffectual prop who should have been removed last year. What I don’t get is why executive producer Nigel Lythgoe won’t cut out these middle men and put the supposedly feuding Minaj and Carey right next to each other and let some real ratings sparks fly. Carey and Minaj come from two very different kinds of stardom and are two very different judges – Nicki is extremely lucid and vivid, while Mariah is very tepid even on a good night.

If Idol finally seems to be recovering from Simon’s 2010 departure it’s because there’s a new queen bee in town. Minaj keeps showing that she’s all about the contestants with her nicknames, spontaneous shout-outs, and alternating nurturing and dismissive attention to them. For instance, the multi-platinum rapper demonstrated keen insight when she told contestant Papa Peachez that he was becoming too complacent and needed “to step up so you can step back”. What could have been a kooky sideshow act made clear Minaj really knows what she’s talking about even if she didn’t enter the big leagues until a remix of Carey’s 2010 single Up Out My Face and a Super Bowl appearance alongside Madonna that served as her entree to Middle America.

It must drive Carey’s reps crazy that Minaj leaves her looking so saccharine and schmaltzy. The third best selling female artist of all time in America has a Heaven-sent voice, but she is way out of her league as a judge. A good fingerwagger doesn’t mentor by gushing. A really good competition show judge actually critiques — constructively and coolly. And that is something the textureless and often inarticulate Carey is clearly incapable of.

By contrast, Minaj has made the show watchable again this season. At first, she appeared almost demure despite her wigs and fake Cockney accent. Then Nicki became a verbal ninja, throwing choice words at Mariah and even storming off the set in anger. Carey sought out the gossip columns to play the victim. The controversy, no matter if fake (and my sources say it’s not), pumped up the volume for Idol. Then there was Minaj’s Twitter slapdown of past judge Steven Tyler as a “racist” and telling him to “go f***” himself — over, of all things, a remark about Bob Dylan. And this took place before Minaj had even judged her first contestant.

It’s not that Minaj is the new Cowell. She’s something much more: an evolution of him. Nicki is what we would have if Simon and Paula shacked up and had a kid. I love how Minaj almost always pats down her outfit and hair extensions before applauding a contestant. Or is so obviously disinterested when Urban is speaking. She has none of that cloying desire to have either the judges or contestants like her. She also has an unpredictability that makes it almost impossible not to watch her. Who could have predicted when, last week, this quintessential urban star cooed to a country singer who’d made it through to the finals, “My ladybug. My marshmallow.”  What also makes Minaj a force on the show is that she is a force on the current music scene instead of a decade ago. For context, credibility and relevance, Nicki is the triple threat judge.

For me, Mariah’s flaws were most clearly on display when Amber Holcomb was announced as one of this year’s finalists and Ryan Seacrest prompted Maria for a live authentic response, only to have her blubber, “I can’t even know what to say.” It isn’t that Carey wishes she was somewhere else, it’s just that she doesn’t seem to know where she actually is. Britney Spears could get away with it on The X Factor last season. But with the poised and posturing Minaj just down the table, Mariah’s shortcomings are strikingly evident. Remember when Carey back in January so insincerely told the self-admittedly awkward Charlie Askew that she could “relate” to him? And Minaj made a point of rolling her eyes for all to see? Even on last week’s live finalist show, Carey in that comical Tom Ford outfit showed more cleavage than concern about the contestants in front of her. The singer may think she’s regally rising above all things Idol with her often detached demeanor. But really she looks like she’s just thinking about her $18 million Idol paycheck.