Dialogue and story. That's all they had, they couldn't rely on whizbang effects or CGI to get that across. I'm not saying there haven't been great movies made since then, there have, but to me that period of film-making (I'd say up to the 70's) across the globe produced some of the finest talents.
What we seem to have now is endless comic-book movies with bigger and bigger explosions, tired serial-killer thrillers, torture-pornography horror, and unfunny comedies. There's been very little on release in the last five years that has drawn me to the cinema. And if I see one more remake I think I might give up altogether.