From mainstream Hollywood movies these come to mind .. there are at least twenty more I want to include but this is the bare minimum list I could come up with.
1990 and later
The Shawshank Redemption
Silence of the Lambs
Saving Private Ryan
Memento (included because the movie runs backwards .. the last scene is shown first)
1960 - 1990
The Godfather I (also II and III)
One Flew Over the Cuckoo's Nest
The Deer Hunter
Lawrence of Arabia
Bridge on the River Kwai
The Sound Of Music
Aliens (Alien part II)
Gone With The Wind
To Kill A Mockingbird
Singing In The Rain
North by Northwest
Rope (included because the movie appears to not have cuts but seems one continuous 80 minute long take)
All movies I have written above are significant Hollywood films from acting, directing, editing, screenplay, story-telling point of view
If you enjoy action films I would add Bourne I, II, III
If you enjoy special effects then Terminator I and II
Passengers (2016) is the most underrated recently made sci-fi film I have seen.
Rope, Vertigo, Psycho, Birds show evolution of the psychological thriller genre .. the one I enjoy most. In 1960 people fainted in movie hall after watching Psycho .. shows how far we have travelled .. compare it to Silence Of The Lambs and Dexter (tv series) to get a snapshot of how society has changed in last 50 years.
The Ten Commandments, Ben Hur, Avatar, Titanic, Jurassic Park, Star Wars, 2001: A Space Odyssey, ET, Back To The Future, Interstellar, Inception .... have been omitted from my list .. but are also must watch.
Rosemary's Baby, The Exorcist, Scent Of A Woman, Pursuit of Happyness, Seven, Training Day, Unforgiven, Scarface, Million Dollar Baby, Kill BIll I and II, Matrix trilogy gets special mention.
Throw in some good Dustin Hoffman films like The Graduate, Kramer vs Kramer, Papillon .. some good De Niro films Taxi Driver, Raging Bull .. some apocalypse/dystopian future movies like I am Legend, World War Z, Blade Runner, A Clockwork Orange .. and the list is almost complete.