All About Eve (1950). Awesome cast and story, and one of my favorite movie quotes: "Nice speech, Eve. But I wouldn't worry too much about your heart. You can always put that award where your heart ought to be."

Metropolis

Some good ones there. Casablanca is a no-brainer, obviously. Damn it, I can't sneak in The Manchurian Candidate (being 1962) but an honourable mention. Kubrick's Paths of Glory from 1957 is a corker - and, of course, Spartacus from 1960.

Nosferatu, eine Symphonie des Grauens (1922) - the greatest horror film ever made, and IMO certainly in the top five films of any genre.