They’re all great, but I would go:
Seinfeld > Cheers > Frasier > Taxi.
Cheers might not be 1st only because I haven’t watched it in so long.
Fraser is the only one I watched regularly and particularly liked. Cheers was weird. Taxi had some okay episodes but was mostly strange. And Seinfeld was never really a show that interested me. I only watch now when there was a pretty good episode.
Though I did watch the Seinfeld finale, and it made me wish I was more familiar with the people coming back.
Cheers. It was the last live-action sitcom I watched regularly. I have never watched Fraser, despite enjoying the character when he was on Cheers. Taxi was very long ago and I was only a sporadic viewer. I’ve seen enough of Seinfeld to know I actively dislike the show.
In order: Cheers, Frasier, Taxi, Seinfeld.
Chefeld, Seiners, Frasier, Taxi.