“Should have seen” is strange, I’ll go with titles that, if you are into cinema probably you have heard about?

Citizen Kane

The Seventh Sigil

Apocalypse Now

Vertigo (Any Hitchcock movie really)

Seven Samurai (Any Kurosawa movie really)

Pretty much anything from Buster Keaton

Charlie Chaplin (I guess Modern Times)

The Godfather part I & II

Taxi Driver

On the Waterfront (Peak Marlon Brando stuff)

Some Truffaut stuff (I guess “Day for Night” would be the most relevant here)

Close Encounters of the Third Kind to get pretty much everything interesting from the Spielberg side of things

Man with a Camera (ok this one is not something I espect any conema lover to know, it’s a very early montage wonder from Russia, always good to get back there and get reminded progress doesn’t always go forward)

La Dolce Vita

2001: A Space Odyssey

Shining

A Clockwork Orange

Reservoir Dogs

Lost Highway (The better Mulholland Drive)

Blade Runner

The Matrix

Star Wars

There’s some good newer stuff but it’s much less “popular” so it wouldn’t make sense to expect anybody to know them. Very little new stuff looks like has the staying power to be relevant years down the line.

I guess The Lord of the Rings? But I consider it more of a great book that got a quality adaptation than a ground breaking stepping stone of cinema.

No country for old men, probably.