Fans of I Love Lucy, like fans of Seinfeld, have a handful of favorite episodes they consider classics.
One of the "classic" Lucy episodes is "Lucy Meets William Holden." This episode is acclaimed as a classic because of just one funny moment: Lucy lighting a cigarette and accidently setting fire to her false nose.
Also, "Lucy Does the Tango" has a classic reputation because of a single sight gag in which Ricky crushes hundreds of eggs Lucy had hidden under her clothes.
Seinfeld fans would never consider an episode a classic because of just one isolated gag. In order for a Seinfeld episode to be considered a classic, it must be packed with multiple great gags, all the way through.
By Lucy standards, "The Frogger" should be considered a masterpiece. It had just one hilarious and memorable gag: George playing real-life "Frogger" while carrying a "Frogger" machine across the street.
It is, however, the consensus among most Seinfeld fans (at least the ones in this newsgroup) that the show declined considerably in the ninth season. Yet, by Lucy standards, the WORST Seinfeld episodes are comedy classics. All you need is _one_ good laugh, and it doesn't matter if the rest of the episode is nothing much.
Some Seinfeld episodes are better than others, but the worst Seinfeld episodes are about on par with the best Lucy episodes. Lucy fans who won't recognize this have just not come to terms with the fact that their standards are too low. If one great gag means "classic", then the WORST Seinfeld episodes should all be recognized as classics.