The Princess Bride is a wonder.
Shawshank Redemption is a marvel. Read the short story for extra goodness.
Cool, an underappreciated movie IMO.
“What have you done with our spaceship?” 
A Clockwork Orange.
But if I had to answer this same question for a more sheltered audience: The Shawshank Redemption.
The Producers. Young Frankenstein is a close second.
Me too.
But my runner-up would be Lawrence of Arabia.
Heavenly Creatures
Seven Samurai
Hands down the best action movie ever filmed.
“Fools! Our computers are always invincible. Adjust them to normal!“
You didn’t hear it from me, but SR is a better written movie than the novella, though the novella is outstanding. Frank Darabont is a freakin’ genius; try The Mist if you haven’t (not the TV series).
The Karate Kid (1984)
An inspirational movie about the touching friendship between an elderly Asian man and a young bullied teenage boy. Okay, that sounded better in my head before I typed it out. 
But seriously I was once in a very dark place and, inexplicably, this movie came on the TV and I hadn’t watched it since I was a kid and it legit helped to give me back some perspective and bring me back to a better place.
Goodfellas.
Airplane. Funniest movie ever made.
Predator/Terminator. Followed by The Sterile Cuckoo.
“This had better work. We can’t send anybody else up!”
Gone With the Wind, although I’ve seen it so many times that I can no longer watch it.
I prefer escapist entertainment, so my choice isn’t a great cinematic masterpiece. It’s Weekend at Bernie’s.
Twelve Monkeys
Monty Python and the Holy Grail
True dat. My personal favorite is Phantom of the Paradise.
My kneejerk answer would be The Godfather. In my opinion its a nearly perfect movie and the only time Pacino was truly great. Sometimes I think its Goodfellas.
I swear I like movies that aren’t about the mob too.