Some more from my personal DVD list:
The Blade Runner (already mentioned, but I repeat this one as it is the best science fiction movie ever made in my opinion)
Westworld
The Great Race
The Court Jester
The Wind that Shakes the Barley
Dragonslayer
The Hustler + The Colour of Money (watch in a row)
Murder on the Orient Express
The Three Musketeers (Gene Kelly)
Ladykillers (UK original)
The Last Seduction
Assault on Precinct 13 (the original)
Nikita (the original from France)
Heaven Can Wait
Thin Man Series
Ninotschka
I Heart Huckabees
Fallen Angels
Garden State
The Seven Samurai + The Magnificent Seven
The Private Lives of Elisabeth and Essex
The Sea Hawk
Captain Blood
Casino
American Splendor
American Beauty
House of Flying Daggers
Sideways
The Philadelphia Story
Léon
The Band Wagon
Drop Dead Gorgeous
The Great Waldo Pepper
The Grapes of Wrath
Those Magnificent Men in Their Flying Machines
THX 1138
The Long Good Friday
All That Jazz
Steamboat Bill Jr.
The General
Reservoir Dogs
King of New York
Arlington Road
Fargo
Frantic
The Fugitive
12 Monkeys
The Bridges of Madison County
Insignificance
Don't Look Now
The Last Emperor
Heat
Trainspotting
Midnight Cowboy
Shakespeare in Love
Bonnie & Clyde
Primary Colors
Out of Sight
Get Shorty
Howard's End
Wag the Dog
Grosse Point Blank
Jackie Brown
Pulp Fiction
The Talented Mr. Ripley
American Grafitti
Dogma
The Limey
The Cider House Rules
Bringing Up Baby
Galaxy Quest
Shaft (the original)
Barbarella
The Thin Red Line
Spartacus (the better Gladiator)
The Straight Story
The Blues Brothers
The Graduate
To Be or Not to Be (the orginal by Lubitsch)
Don't Look Now
The Dark Crystal
Keeping the Faith
Hope & Glory
Liberty Heights
The Man on the Moon
Singin' in the Rain
L.A. Story
Lock, Stock and 2 Smoking Barrels
Alien
Being John Malkovich
Akira
Taxi Driver
Sleepy Hollow
The Silence of the Lambs
Raging Bull
Heaven's Gate
A Clockwork Orange
Full Metal Jacket
The Sting
One Flew Over the Cuckoo's Nest
Misery
Manhunter
Stand By Me
Midnight Run
Snatch
The Remains of the Day
The Truman Show
Sabrina (the original)
The Fabulous Baker Boys
Gangster No. 1
Traffic
Crouching Tiger, Hidden Dragon
The Deer Hunter
Driver
The Wonder Boys
3 Days of the Condor
Some Like It Hot
Outland
The Time Machine (1960)
A Fish Called Wanda
The Right Stuff
Almost Famous
Thirteen Days
Do the Right Thing
Ride With the Devil
Death on the Nile
The French Lieutenant's Woman
Marathon Man
The Ice Storm
Apocalypse Now
The Pledge
Le fabuleux destin d'Amélie Poulain
M*A*S*H
Memento
Tron
Hana-Bi
Sonatine
Vanishing Point
The Usual Suspects
Rear Window
North by Northwest
His Girl Friday
Road to Perdition
Dead Poets Society
Citizen Kane
Miller's Crossing
Rushmore
Who Framed Roger Rabbit?
Annie Hall
Charade
What's Up, Doc?
Fear and Loathing in Las Vegas
To Kill a Mockingbird
The Andromeda Strain
Fahrenheit 451
One, Two, Three
The Fisher King
Brazil
The Name of the Rose
Serpico
This is Spinal Tap
To Live and Die in L.A.
The Omen
Ran
Rashomon
The Fearless Vampire Killers
Les Triplettes de Belleville
Volver
La mala educación
Todo sobre mi madre
A Man For All Seasons
The Nutty Professor (the original)
Goodfellas
A Night at the Opera
Monkey Business
The Great Dictator
And I also highly recommend every short & long movie by Laurel & Hardy (I got 27 L&H DVDs and every single is worth it) as well as all of Chaplin's and Keaton's silent shorts.
And last but not least the Tom & Jerry cartoons from the 40s and 50s - the best cartoon series ever made is available on 12 DVDs.
