No one I know has seen Seinfeld.

Of course the Italian dubbing is bad, doesn't capture the spirit of the underlying humour at all (I watch everything in its original version, even if I don't know the language, and of course, in the latter case, if Italian or English subs are available). That's true for most sit-coms, both past and contemporary ones. Besides, I think a show like that appeals to people keen on mostly subtle humour, not exactly belly-cracking funny. And I can understand how Seinfeld might not be that popular here, there probably are cultural reasons (for example, people pointing out "not much happens" in most episodes, as well as "Seinfeld plots don't deliver a moral"). A show like Friends, for example, is definitely more universal, and appealing to a much larger crowd (outside the most educated areas of USA, at least).