Catcher in the Rye was always an unforgivable whiney crap-mound of a book. Its notoriety is based on its banning, and the larger issue of whether people should be allowed to read books with swears, misanthropes, and sexual references in them, but there are and were so many better books featuring those things out there.
Family Guy is a fascinating case of a crappy show insisting upon itself so hard that it successfully got itself uncancelled and forced into pop culture as a zombie endlessly repeating itself on the level of its inspiration and closest rival The Simpsons.
I also loathe Grease but its general appeal is pretty easy to explain: it came out in the 1970s as a rose-tinted nostalgia piece for white middle-class boomers who grew up in the 1950s and, as so many people of all ages do, idealized their childhood era as when things were so cool and simple. (Spoiler to folks of all eras: things weren't actually any simpler when you were young, you were just shielded from more of the bullshit than you are now.) It was the same nostalgia that fueled the runaway success of Happy Days on TV in that era, though at least that show managed to be a functional sitcom with more substance to it than the empty-headed misogyny-flavored story of Grease.