The main advantage of choosing "vintage" films for kids or for general viewing is that one can make selections based on historical critical and popular consensus.
Flops at the box office don't necessarily mean a film isn't worth watching. More telling are films, esp. big budget films, that aren't worth watching. YMMV.
Wiki's list. One of several online opinions:
List of films considered the worst - Wikipedia, the free encyclopedia
Some of the listed films are so bad, they border on parody. Yes, I saw a few of them, but mostly on the tube.
Sherwood