I never did watch The Tonight Show again after Leno got it. Just never warmed up to him. But I never watched Letterman much either. Neither of them had the class that Johnny Carson did.
What they didn't (and couldn't have) were characters like Art Fern, Floyd R Turbo, El Mouldo or Carnac the Magnificent.
Leno's Cop and Kitty was OK but Carnac defining Sis boom Ba as the sound of an exploding sheep was genius.