In no particular order . . .
CASABLANCA - see article below dedicated to this all-time Hollywood classic.
CITIZEN KANE - Orson Welles was the star, producer & director at a mere age 25. The movie was controversial as it supposedly paralleled the life of William Randolf Hearst of the publication world. The film was originally released in 1941, and for that reason (the war) it wasn't seen by a lot of movie houses. After the war it was re-released & it took off like wildfire . . . R-O-S-E-B-U-D ! ! ! (Remember that name...)
CALIGULA - "When in Rome . . ." this is Penthouse founder Bob Guccione's depiction of the most sexually depraved society of all time at it's most extreme (I included this one on a dare.) The Roman Empire was never portrayed in more vivid realism - if you want to see Rome, see this movie.
LAWRENCE OF ARABIA - An English guy who fought the Turkish, Lawrence was a candidate for Post-Traumatic-Stress-Disorder Poster Boy. A fantastic story, an incredibly well-made movie experience.
LORD JIM - Joseph Conrad's masterpiece brought to screen. Another Conrad-inspired story made this list, do you know which one?
THE PATRIOT - Given the way things are going against those who would call themselves patriots . . .
RAN - Akira Kurasawa's version of King Lear, set in medieval Japan. Armies of samurai hacking each other to bits.
APOCALYPSE NOW - Best War Movie of All Time (BLACKHAWK DOWN is a close second for this title); War is stupid, and dodging bullets cannot be replicated in a theater, so why not go all-out insane and make it a good show?
BEN HUR - 11 - count 'em - ELEVEN Academy Awards; the chariot race alone is worthy, and then there's the sea battle.
THE GREEN BERETS - (or just about any movie with John Wayne) Based on a true story, it demonstrates the bias of the left media 40 years ago - they should update it for Iraq/Afghanistan and re-release it; nothing has changed with left-wing media bias.