Cain vs. Abel. Frasier vs. Ali. And now, in this corner, another duel for the ages: Joan Rivers vs. Annie Duke.

NBC's Celebrity Apprentice has been providing some of the most jaw-dropping television of the season. And, I'm happy to say, it's not over yet. Last week was the best, most riveting, most unbelievable episode of Donald Trump's TV show ever broadcast -- and the two main combatants, comedienne Rivers and poker champion Duke, both survived to fight another day...

This season of Celebrity Apprentice (Sundays at 9 p.m. ET) started with larger-than-life characters being eliminated quickly: Tom Green for being too goofy, Dennis Rodman for being too inebriated and surly, Andrew Dice Clay for being too... Andrew Dice Clay. But those were undercards to this season's championship bout.

"I'm going to crush you, Joan," Annie Duke informed her rival, when the two of them agreed to be project managers of their respective teams on a charity auction task. Nice talk. But it was said with a smile. And in any event, it was a lot nicer than when Rivers, in the boardroom after her loss, compared Duke to Adolf Hitler. Really.

"She does seem nice to me," Trump said of Duke, after hearing Rivers toss some insults her way.

"So does Hitler at Buchenwald," Rivers shoots back.

Morgan was equally thrown by Melissa Rivers' constant defense of her mother's actions and comments, and criticisms of Duke, even though the younger Rivers was on Duke's team. "I find this dynamic fascinating," Morgan admitted, challenging Melissa Rivers' conduct. "You would speak up and knife your leader to suck up to your mum."

Morgan was right on the money questioning that dynamic. So was Ivanka Trump, who has matured, since first coming aboard as one of her father's TV lieutenants, into a very poised and precise presence on the show. When she asked Joan Rivers about her feelings if Joan outlasts her own daughter on the show, Joan said it would be okay, so long as Melissa lost fairly rather than being thrown under a bus.

"If I were thrown under the bus," Ivanka replied with a cool, knowing smile, "my father would be disappointed in me for allowing myself to get in the way of that bus." Great stuff. This far into the game, there are two official teams (KOTU, with Joan Rivers and Clint Black, and Athena, with Annie Duke, Melissa Rivers, former Playboy Playmate Brande Roderick and Jesse James). There's also a third, unofficial team: the Rivers running through it.

Donald Trump's firing decisions, while seeming capricious on occasion, always make sense in the larger picture. And because he IS in charge, I have little doubt of this season's outcome. When you have competitors as naturally vehement towards one another as Joan Rivers and Annie Duke have grown to be, they almost have to reach the final. Otherwise, any other climax would be more of an anti-climax.

But if it goes to a Duke vs. Rivers title card, what an ending that will be, and what a ride until then. "She's a crazy bitch," Annie Duke said of Rivers afterward. And Rivers, on her own Twitter mini-blog, posted the following: "I just compared Annie to Hitler and I feel terrible. My apologies to Hitler."

Melissa Rivers, who should have gone home weeks ago, eventually will be fired, which should make for two levels of drama. And if the final task mirrors the celebrity auction, where Duke's wealthy friends flew in to support her while Rivers saved her team's presentation but raised little money, this contest could well get down to, instead of how many people you know, how many friends you have.

For the record: My money's on Annie Duke -- to go all the way, and to win this thing, deservedly. She's come off as smart, determined and charming. Both generations of Rivers, by contrast, bring to mind three very different adjectives: stubborn, abrasive and co-dependent.

Also for the record: Donald Trump, with this season of Celebrity Apprentice, already is in the winner's circle. And why not? His show is better than ever, and his daughter radiates beauty and intelligence in equal proportions.