Since I have (older) kids, I can add another layer to the analysis of “timeless” movies, because for me, they would be movies that would still hold the attention of my kids.

A lot of good ones have already been mentioned, but I would like to submit “Independance Day”. Yes, it is cheezy at times, but not because of its age, it always was that way. It held my kids interest. They noticed that none of the people running from the alien ships had their phones out, because smart phones didn’t exist yet. And I found that they already knew the most impactful points, because of all the memes.