Even though SNL is built around comedians and comedic actors, it is really all about the writers. Occasionally you get a Farley/Hader/Hartman where they can transcend a skit. But mostly you get folk like Kenan or Sandler who can add flourishes but really need a solid “script” to work off of.
But EVERYONE (… except MAYBE Farley) live off of the writers. People like Tina Fey and, funny enough, Conan who can make those gags t hat stick with you forever.
I am not a fan of Fallon but he has that “empty vessel” vibe to him. Give him a good writing team (… and he’ll be an asshole to them. Err) and he can fill the time in between the press pieces for actors.
Which is more or less what the Leno/Fallon style late night show is. It is a stand up segment that makes you understand why Seinfeld would open with that trash for so many years followed by mostly smiling and nodding as an actor or actress talks about their movie and plays a clip.
Personally? I always preferred the Conan/Ferguson approach. Similar structure but the comedy and riffing continues well into the interview and the actor/actress is expected to join in. Sometimes it is incredibly awkward, sometimes it makes you wonder just how much certain people knew, and sometimes it is a truly spectacular conversation that gets to the heart of the business. But I can also get how a studio might not appreciate the same Mac and Me clip being aired for the hundredth time for the movie they just spent hundreds of millions of dollars on.
And then you have people like Letterman/Colbert/Meyers who are very much in that middle ground to the extent that “everyone likes them”