I personally feel like Seinfeld was such a lucky hit - the right writers, ensemble, time, etc. - that something was created that truly stands the test of time. How the hell this show is so damn relevant in 2022 and speaks to modern US culture, idiosyncrasies, politics, etc. is astounding. Shows like Friends will always have lifelong fans and be running on TV for decades to come, but I'd be hard-pressed to agree that there are many if any shows before 1989 that are as on topic and relevant to today as Seinfeld.
For that reason I hate to choose a simple line or scene. But I'll choose 3 lines that come to mind. Not the absolute funniest or craziest or scandalous, but 3 examples where I feel the characters and writing and topics were "just right".
"Do women know about Shrinkage?" "Why does it shrink?" It just does....."
George & the Cleaning Lady - much like the universally loved Contest episode, I loved the premise. That George not having sex was making him smarter. When he shows up to the club to open for Jerry, and he's back to being a lovable idiot, Jerry knows he ended up giving in and having sex. George's "was that wrong" was perfect. It also happens to be Jason Alexander's favorite line of the series.
Anti-Dentite - "Dentists" "Yeah who needs them? Not to mention the Blacks and the Jews"
I mean cmon, is there anything more Seinfeld then closing with a bigoted comment and racist joke by Debra Messing?