Lots of discussion has been going on about Seinfeld vs. Mad About You vs. Frazier. Thought I'd add my two cents worth in about what I think makes a comedy series funny. (In other words, why Murphy Brown sucks:-) )
To be funny, a series must either have good, solid character development through dialogue, or be just totally off the wall. Development through dialogue means that the communication between characters is "realistic"; the characters actually communicate, and say humorous things that might be said in real conversation and that is relevant to the "situation" of the show. MASH, All in the Family, Mary Tyler Moore, and Cheers (to a lesser degree) all had this. You got to know the characters and care about them. They had real things to say and humor came from real life sarcasm found in everyday conversation. Bad comedy shows are ones in which the humor is all set up. I used to watch Murphy Brown now and then with a housemate who loved it. I found I could almost verbatim quote the dialogue before it was even said, simply because it wasn't communicative dialogue between people, rather it was set-up stand-up comedy put in a sitcom environment. (And bad stand-up at that.) That's the problem with most "comedy" sitcoms: the lines they speak could be transfered to any show, and they are meaningless. The other option is total silliness: The Simpson, Get a Life (with Chris Elliot). These are funny because the are intentionally stupid, and don't have any pretense of serious developmental dialogue. (Married With Children is like this too, if one doesn't mind its offensiveness.)
Seinfeld in some way covers both these criterion. The dialogue is realistic, in that it does deal with everyday topics, and there is character development. Indeed, the dialogue is precisely what makes Seinfeld funny. The silliness comes from the fact that complete goofiness is incorporated into everyday drudgery. (The Pez Dispenser, The Nose Job, etc.) Oh yes, I also like Mad About You; they say things to eachother I could see actually being said between recently married people. Frazier, on the other hand, is dangerously close to the set up sitcom a la Murphy Brown.
That's all
Mark