Seinfeld 68th is like DeBruyne or Kompany being voted 68th on the best players ever for City list.
Now obviously I wouldn't expect over-the-ponders to be as familiar with it as Yanks, nor to pick up on all the subtleties that are uniquely American, and New Yorkian (even though it was filmed in LA) -- there's a lot of baseball humo(u)r, e.g. But still -- somehow the Young Ones and Cheers are going to be ahead of Seinfeld, to name two off the top of my head, and while both are good IMO, neither holds a candle to Seinfeld.
Out of 180 episodes (180!), there are going to be a few that are meh, especially early ones. But at least one-third of the episodes are brilliant, and most of the rest are very good and very funny.