Are we talking what is our own personal greatest or what would be considered the greatest?
If its critical acclaim and longevity then you gotta go with shows like MASH, Hill Street Blues, Gunsmoke, Cheers, The Simpsons and Seinfeld.
Cant discount The West Wing for winning 4 straight years for best dramatic show on TV.
Family guy, Babylon 5 and those type shows are going to be huge among AT'ers but not across the country.