I have a hard time watching many, but not all, movies that debuted prior to 1980, maybe even 1990. I'm drawing a blank on the 80s. The only ones I can think of at the moment that I would recommend are Trading Places and Dirty Rotten ScoundreIs. I especially struggle to enjoy 60s and 70s cinema.
While I did like treasure of the sierra madre, it didn't leave enough of an impression on me for me to post it.
Godfather trilogy: 2nd one was great. 1st was OK and 3rd was meh. Apparently, Copolla needed the money due to some massive flop he made, otherwise, Godfather III never gets done.