01/30/2014 08:05 pm ET Updated Apr 01, 2014

Jay Leno's Tonight Show Legacy: It's the Viewers, Stupid!

On Feb. 6, Jay Leno will host The Tonight Show for the last time, leaving behind an amazing legacy to late-night television where he has reigned at the top of the Nielsen Ratings for almost two decades. The numbers for his current, and last, season on Tonight have been his best in three years. I don't think any other late-night host could ever match Leno's incredible record.

And yes, I believe that makes Leno the King of Late Night, even though TV critics and writers would shudder at the thought. From the beginning they considered him too bland to be worthy of Johnny Carson's throne, and many assumed he wouldn't last. Needless to say, they were wrong. Leno will have done 4,610 episodes when his show, which has aired 22 years, wraps. That's 79 more episodes than Johnny did in 30 years.

But Leno can handle the critics. His problem has been NBC's executives, who have never appreciated his uncanny ability to play to a mainstream audience better than anyone else in show business. To Leno, it has always been the viewers, stupid!

Getting by on three to four hours of sleep a night, he has obsessively devoted himself to his daily monologue, editing 1,500 jokes down to 25, which have been chosen to appeal to a wide spectrum of people. For every smart joke he does a silly one. He constantly tests material on staff members, from production assistants to producers. If you walk by his office, chances are, he'll call you in to run a joke or two by you.

Despite Leno's stellar ratings, NBC brass fired him twice. As Leno's co-producer, I was there the first time, when Jeff Zucker, then president of NBCUniversal, told him Conan O'Brien would be replacing him. Leno, normally philosophical, was visibly upset, as he explained to my colleagues and me there was nothing he could do. Just as he described it to Steve Kroft on 60 Minutes, Leno talked as though he had just been jilted by a lover. "Once the girl says no, you just have to accept it. She's never going to change her mind," he said.

Entertainment writers, Letterman and O'Brien would eventually describe Leno as a weasel who took away O'Brien's The Tonight Show gig. Actually, it was O'Brien who was responsible for that. He could never appeal to a broad audience. In his seven months as Tonight Show host, O'Brien lost 50 percent of Leno's audience. But hey, critics loved CoCo.

Following his disastrous prime-time stint at The Jay Leno Show, Leno was given his old job back at Tonight where he restored the ratings to number one within one month. As his show entered the home stretch, Leno has delivered some of his best performances ever with pointed monologue jokes about President Obama, which have resonated with many viewers.

To Leno, it's about carrying on the tradition, started by Carson, of lampooning whoever is in power, while other late-night hosts, particularly Letterman, have avoided doing Obama jokes until recently. Which raises the question: Does that make Leno edgy and Letterman milquetoast? Just asking.

When Comcast acquired NBCUniversal from GE, the new executives fired Leno and replaced him with the younger and hipper Jimmy Fallon. Leno, who had obviously been through this before, accepted the news graciously, and has been very supportive of Fallon.

Unlike O'Brien, Fallon actually has wide appeal, but I think Comcast's decision was shortsighted. Fallon's only 39, and he wasn't threatening to leave. So why get rid of the number-one guy when he's still at the top of his game? We'll see how Fallon does in the crowded late-night environment where he's a crap shoot and Leno's a proven winner.

What's next for Leno? Will he just do stand-up appearances and work on his cars? Not a chance. I worked with him at The Tonight Show for 18 years. He has the mentality of a boxer. In fact, boxing is the only sport he really likes. No boxer would ever walk out of the ring in the middle of a fight in which he was pulverizing his opponent.

Leno said he won't do another Tonight Show, and I believe that's true. But he loves doing a daily monologue, and I don't think he would give that up if an opportunity, such as CNN or another cable network, presented itself. Did I say "if?" I meant "when."

Dave Berg was a co-producer at The Tonight Show with Jay Leno. His new book, Behind the Curtain: An Insider's View of Jay Leno's Tonight Show, will be released by Pelican Publishing this spring.