When Jay first took over the "Tonight Show" from Johnny Carson he really seemed new, fresh and cutting edge. Now he is very predictable. The jokes are much safer and the skits are all repeats.
He has reached a level of saturation in the American culture that he and the show are thought of together. People in the business refer to being on "Leno". If you are unsure if someone is an actual celebrity, a comment like "he's been on Leno three times" will settle it.
Jay's funny. Jay's predictable, but we will keep watching. I like Dave better, but Jay is okay. Dave has the gap in his teeth, Jay has the chin. Take your pick.