Note: This list won’t include any Hitchcock films, which need their own list.
1. Wizard of Oz (1939): Not only is this a great, great film, but it's the cultural granddaddy of them all - you almost can't watch a movie or television show today without seeing some reference to this film. This is a must see and I like to watch it at least once a year.
2. The Bogarts: I’m grouping these all at once so they don’t dominate the list. Here are my favorite Humphrey Bogart films in order:
The Maltese Falcon (1941): This film IS noir. Nothing else comes close. The story of a group of unsavory people who are seeking a fabled golden bird that has been stolen and re-stolen many times over the years and which just happens to fall into the lap of detective Sam Spade. With a great cast and all kinds of interesting undertones, this is a fantastic film.2. The Adventures of Robin Hood (1938): Starring Flynn as Robing Hood, Olivia de Havilland as Maid Marion, and some lesser-knowns like Basil Rathbone, Claude Rains and Alan Hale, this is THE Errol Flynn film. Both a rousing adventure, a romantic love story, and a showcase for Flynn's charm, this is another can't miss.
The Big Sleep (1946): Another Bogart detective film, this one is much more complicated than anything else Bogart has done and it's full of great performances and tense moments... and a few errors.
The Have and Have Not (1944): This one is just fun as Boggie and a very young Bacall play a romantic cat and mouse in occupied Martinique.
The Caine Mutiny (1954): Probably Bogart's best performance as the tyrannical Commander Queeg who panics and must be replaced by his crew during a typhoon, only to have the court martial that follows not turn out the way the audience expected. This is an excellent, excellent film.
Treasure of the Sierra Madre (1948): The only Western I've seen Bogart do, this one is truly memorable and has some amazing moments as the three friends search together for gold and then turn on each other once they strike it rich.
Key Largo (1948): Boggie a coward? It seems that way when he finds himself held prisoner in a hotel by Edward G. Robinson as a hurricane is about to strike, and Boggie won't stand up to defend the people he's trapped with.
Casablanca (1942): Often voted the best film ever, I truly enjoy this film, but honestly, it feels a little light compared to the other Bogart films.
3. High Noon (1952): Gary Cooper plays Marshal Will Kane who has lost his nerve and learns that the people he's defended all these years are deeply ungrateful when it comes time to help him. This is a great character study and it's a powerful film when Cooper stands up in the end.
4. Forbidden Planet (1956): Leslie Nieslen in a serious role? Yep. This is probably the strongest science fiction entry in Hollywood's catalog until 2001, as Nielsen and crew find Dr. Edward Morbius (Walter Pidgeon) and his daughter alone on a planet that once belonged to the Krell, before they destroyed themselves somehow.
5. The Bridge on the River Kwai (1957): This is just an awesome movie all around. You have amazing cinematography from David Lean, a tremendous performance from Alex Guinness as the British commander who lets his pride overwhelm his judgement in a Japanese prison camp as the Japanese use the British prisoners to build a railroad, and strong supporting actors.
6. Gone With The Wind (1939): This film has proved so strong and so enduring that it's defined the antebellum American South for most people.
7. Spartacus (1960): Kirk Douglas stars as escaped slave-turned-general Spartacus as he battles Romans for the very survival of his army of slaves and romances Tony Curtis... uh, the girls. Anyway, this is one of Stanley Kubrick's best and you can't swing a crucified slave without hitting a famous actor. Highly recommend.
8. It’s A Wonderful Life (1946): Sappy, depressing and yet deeply heartwarming, this is one of Jimmy Stewart's best films as he contemplates what the world would be like without him around.
9. His Girl Friday (1940): Cary Grant and Rosalind Russell in an unforgettable romantic comedy.
10. Ben-Hur (1959): Staring Charlton Heston, this is the story of Juda Ben-Hur, and it's truly epic. Pry my chariot from my cold dead hands.
And of course, don't forget things like the Marx Brothers or war films that may have already appeared on other lists like Sergent York or All Quiet On the Western Front.