The thing about Seinfeld is that for it's time it was fantastic with little to no competition.
The 80s/90s crossover generally only had Cheers, Roseanne, Murphy Brown and Seinfeld which were more adult-focused, as opposed to the syrupy family stuff like Full House, Blossom, and Step By Step.
93 onwards stuff like Frasier and Friends took off, and many other strong sitcoms hit their stride.
Obviously Americans, or those brought up on American TV (like us dirty South Africans) probably had Seinfeld resonate with us more than the Brits would.