A couple of my favorites started in the late 70s but ended in the 80s. I don't think I watched any in the 90s but maybe you guys will remind me of some.
Night Court (which I had forgotten about until our new thread reminded me)
One Day at a Time (started in the late 70s)
WKRP in Cincinnati (started in the late 70s)
What surprises me is that two of these are family sitcoms, which I would have told you I never watch. Usually I prefer to watch shows about people at work, which covers a lot of territory if you think about it. Shows about people at home typically bore me. But One Day at a Time and certainly Family Ties feature intelligent characters and I think that was their saving grace with me. I hate shows about unusually stupid people.
Three family sitcoms I hated with a passion were -
Everybody Loves Raymond
Fresh Prince of Bel-Air
If there is a hell, my portion of it will have these three shows playing nonstop. All three were 90s shows, interestingly. Also all three featured unusually stupid people.
Seinfeld is the only one I watch to this day if it is on and it stands above the rest IMO. That said I lived for sitcoms of the 80s and 90s. I enjoyed The Cosby Show, Roseanne, Fresh Prince, Cheers, Wings, King Of Queens, Night Court, Everybody Loves Raymond and Family Ties and Taxi, and even Blossom. I hated Friends while it was on but now I don't really care either way about it.