My wife & I have been watching this: https://www.amazon.com/Hollywood-Idols/dp/B071CLQBXZ and it has reminded us of what American movies used to be. We've watched them all and if i had to pick just one to illustrate the entire range of acting, it would be Jack Lemmon's episode/segment.
I'd like to add to blues' list - absolutely anything by Mel Brooks.
I would also add the first "National Lampoon's Vacation" and "Christmas Vacation."