The Princess Bride

• Monty Python and the Holy Grail
• The Big Lebowski
• Inception

Edit: Can't believe I left these out:

• High Fidelity
• Princess Bride

Because I haven't seen it mentioned:

They Live

Terminator and Terminator 2: Judgement Day

• The Fifth Element
• Big Trouble in Little China
• LOtR
• Akira
• Up

Princess Mononoke

• The Thing Carpenter's version
• Shawshank Redemption
• Yojimbo
• The Seventh Seal
• Duck Soup
• No Country For Old Men
• The Naked Gun
• Back to the Future
• The Guest
• Shrek
• The Hunt for Red October
• The Blues Brothers
• Dark City
• The rifftrax version of Jaws
• Double Indemnity
• Lord of the Rings trilogy
• Hot Fuzz
• The Dead Don't Die
• Hunt for the Wilderpeople
• Free Solo
• In the Loop
• Evil Dead original
• Office Space
• Rosencrantz and Guildenstern are Dead
• The Cabin in the Woods
• Clue
• North by Northwest
• Brick
• The Sting
• Return of the Jedi
• Casablanca
• The Third Man

Most of mine are already listed but here's a couple more.

Army of Darkness

Dogma

The Protector

Clue

Full Metal Jacket

One Flew Over the Cukoo's Nest

Howl's Moving Castle

Four Rooms

Pulp Fiction

Idiocracy. It was funny when it came out. Now it hurts.

• Caddyshack
• Animal House
• Goodfellas
• The Godfather
• Shawshank Redemption
• Schindler’s List
• The Shining
• One Flew Over the Cuckoo's Nest

Big Trouble in Little China

Princess Bride

Romancing the Stone

The Shining

Full Metal Jacket

Memento

No particular order. Also, it’s movies that I watched, can’t speak on essentials that I might be missing.

It’s kinda hard to make a list on essentials tho. Because your personal taste obviously plays a big role. I can’t see my girlfriend liking more than 10 percent of those…

Schindlers List

Gladiator

No country for old men

The grand Budapest hotel

The big Lebowski

The Fellowship of the Ring, The Two Towers

Star Wars (the original one)

Requiem for a dream

Pulp fiction

The good, the bad, the ugly

The lives of others

La vita é Bella

All quiet on the western front (1930 version)

The dark knight

The Truman Show

2001: Space odyssey

Alien

7 Samurai

Princess Mononoke

Trainspotting

Boyz N the Hood

Scarface

The Godfather 1, 2

The Matrix

Clockwork Orange

Shutter Island

Kingdom of Heaven

Wolf of Wall Street

Honorable mentions because they are popular and everybody always talks about them (I like a lot of them, too. Don’t consider them essentials tho):

Inception

Interstellar

Fight Club

Harry Potter

Return of the King

Rest of Star Wars (whatever people consider the good ones at last)

Saving Private Ryan

Django Unchained

Toy Story

The Lion King

• Airplane!
• Ghostbusters
• ~~The Naked Gun~~ (Already mentioned)
• Gremlins + Gremlins 2
• Indiana Jones and the Temple of Doom + Raiders of the Lost Ark
• The Great Dictator
• Forrest Gump
• American History X
• Grave of the Fireflies
• Rear Window
• The Silence of the Lambs
• Braveheart
• Highlander
• ~~Resevoir Dogs~~ (Already mentioned)
• ~~Children of Men~~ (Already mentioned)
• ~~My Neighbor Totoro~~ (Already mentioned)
• The Exorcist
• Rambo: First Blood
• Groundhog Day
• What’s Eating Gilbert Grape
• Scent of a Woman
• Predator

American History X and The Green Mile

• The Thing ('82)
• Hot Fuzz
• Mad Max: Fury Road
• Spirited Away
• Taxi Driver
• The Matrix
• Unforgiven
• Nosferatu
• Suspiria ('77)
• 12 Angry Men
• Psycho
• The Wizard of Oz

Donnie Darko

Office Space

Equilibrium

Amélie

Back to the Future

Big Trouble in Little China

Fear and Loathing in Las Vegas

Brazil

A Clockwork Orange

12 Monkeys

The Abominable Dr.Phibes

Just off the top of my head: Alien and Aliens are wonderful, Apocalypse Now needs no introduction, Interstellar, 2001: A Space Odyssey, and finally Oppenheimer, which is one of the best movies ever made in my opinion (what can I say, I'm a sucker for an incredibly well-told story).

12 Angry Men

My Neighbour Totoro

Memento

Wall-E

The Truman Show

Eternal Sunshine of the Spotless Mind

"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.

Alien, Aliens, Alien3.

Rashomon

Man with a Movie Camera

Battleship Potemkin

Metropolis

The Lost Boys

The Matrix

Withnail & I

Requeim for a Dream

Synecdoche, New York

Hero

Let the Bullets Fly

Jackie Brown

Anomalisa

The Skin I Live in

Parrallel Mothers

Martyrs

Amélie

Taxi Driver

Etneral Sunshine of the Spotless Mind

The Lighthouse

Everything, Everywhere, All at Once

A New Hope, Empire, RotJ (despecialised, or original cuts

Bladerunner, Bladerunner 2049.

The Orphanage

Watership Down

Donnie Darko

American Beauty

I'm All Right, Jack

The Great Dictator

Blow-Up

City of God

Amadeus

Seven Samurai

Lust for Life

District 9

Network

The Road, so people should know what to expect in a decade or so.

Krull is one that stays in all my libraries. It's so obscure yet has names like Liam Neeson, Robbie Coltrane, and David Battley. It was my dad's favorite movie.

• Lord of The rings Trilogy
• All Quiet on the Western Front
• Princess Bride

Office Space - the message was ahead of it's time 12 Angry Men – reactionaries vs rationality

Santa Sangre (1989)

Little Shop of Horrors (Director's Cut) (1986)

Sorcerer (1977)

The General (1926)

Hunt for the Wildepeople

https://www.rottentomatoes.com/m/hunt_for_the_wilderpeople

The Truman Show

Yeesh, apologies for crappy formatting

Matrix

Alien/Aliens

Spirited Away

The Dark Knight

The Shining

Heat

Wall-E

Memento

Jurassic Park

Apollo 13

Children of Men

Unbreakable

Hereditary

The Witch

Arrival

Thin Red Line

Sixth Sense

Terminator 2

Primer

Finding Nemo

I could keep going

Secretary (2002)

Think what you want, this movie has layers of depth to it. Every time I watch it I feel like I learn something new about a character and why they are the way they are.

Star Wars (Original Trilogy)

Lord of the Rings Trilogy

Indiana Jones (first 3 movies)

I can't believe no one has said Tucker and Dale vs Evil yet. It's best if you watch it without knowing anything about it beforehand.

Equilibrium or The Fountain

Puss in Boots: the Last Wish turned out to be really good, imo.

Harold and Maude (1971)

• Perfect Blue
• The End of Evangelion
• Love & Pop

Just gonna name a few ones that weren't mentioned yet that I find noteworthy, unique and/or just pure fun:

• The Boy and the Heron (2023)
• Parasite (2019)
• The Grand Budapest Hotel (2014)
• The Man from Earth (2007)
• Ratatouille (2007)
• Catch Me If You Can (2002)
• The Sixth Sense (2001)
• The Emperor's New Groove (2000)
• Playtime (1967)

I haven't seen it posted here yet so I'd like to add one of my favorites, Big Fish.

Interstellar

Unironically: Star Trek IV: The Voyage Home

A lot of movies already mentioned, so I'll add two movies which I feel are essential to watch:

• Ex Machina (2014)
• Into the Wild (2007)