I can't stand Fallen, I never ever watch him !After you've seen Carson, why watch a bunch of late night hacks??, they have No talent.
Late night TV existed before Johnny and continues since his departure, there is no question he reinvented - and in many ways created the genre. He is undoubtedly the king! He brought a certain class while remaining creative, funny irreverent, and racy. He could communicate volumes with a smile, a smirk, a hand gesture (golf swing), or just the twinkle in his eye.
With that said, I am addicted to late night TV so I watch all the shows except Letterman. I used to watch Letterman religiously when he was on after Carson but in the last few years he's become stale, repetitive, bitter, and highly political - all things Johnny never did.
There have been a lot of great drummers on late night TV - Shelly Manne, Ed Shaughnessy, Louie Bellson, Steve Jordan, Anton Fig, Max Weinberg, Questlove, etc.
And you get to see them every night. In addition often good guest bands.