The Secret of Fawlty Towers
Was not only the great writing and acting, but they knew when to quit.
I'm sure by today's PC standards picking on poor Manuel from Barcelona wouldn't be tolerated, but he sometimes had the best lines/acts.
I also have trouble imagining it ever working as an American production. Look what happened to Coupling, as one example. And I am sure that Basil would be considered just too harsh.