Let me add my voice to Sports Night, but I've got a couple others...
fearofmear, I couldn't agree more about Cupid! One of the best shows ABC has ever cancelled. I've got every episode on tape. I only wish the quality was decent.
The_Jazz, as an ex-radio guy, I loved WKRP. Probably my favorite TV show of all time. ("I want a hat!! Cops gotta hat. I want a hat too!") Fortunately, the show had a good run and left right before it really jumped the shark, though you could see the fin circling in the water.
Others:
Quantum Leap
Class of 96 - loved, loved, loved this one! But I'm probably dating myself real bad here.
Police Squad - yeah, the movies are old hat now, but the show's six episodes were gold.