What are they?

And also what are some underrated/forgotten sitcoms?

I always think of Cheers as one of the GOAT sitcoms. Probably the funniest character writing and all around performances, especially Shelley Long.

The UK sitcom Ever Decreasing Circles is underrated. The premise is really simple - an uptight man becomes obsessed and insecure about his successful new neighbor, but the execution is perfect. Its a deconstruction of suburbia and middle england politics.