Average standup comedian before he got his own show. The real stars of the television show were the characters Kramer, George and several of the side characters, especially Newman. Seinfeld himself (and Elaine) are not all that funny. I also suspect that Larry David was the real creative genius behind this show.
I tried. I really tried to get into Letterman. I remember watching him almost every night for about six months while I was in grad school. I learned that he is not only not funny, he is also an egomaniac in love with the sound of his own voice. It is often clear that he is not the least bit interested in what his guests have to say. I got the strong impression that his popularity originally stemmed from being some sort of anti-Carson, the underdog. It became "cool" to like Letterman.
Another mediocre standup comedian who managed to get his own show. Only, the show is only about half as funny as Seinfeld.
Was never funny. Proof that people will watch whatever you throw in front of them. Yes, I understood what he was trying to do. No, it wasn't funny, or even all that clever.