There is perhaps no movie genre more prolific or more full of groundbreaking masterpieces than the drama genre. This is a vast, incredibly expansive category that can cover all the way from action thrillers to grounded arthouse films, but for variety and fairness' sake, this list will only contain movies that aren't intensely genre-driven. As such, revolutionary masterpieces like Seven Samurai and the Lord of the Rings trilogy are a topic for another day.
That still leaves not just one, but several of the greatest artistic achievements in the history of cinema as a storytelling medium. These are gems from all throughout history and from all over the world, whether it's a modern Brazilian masterpiece like City of God or a Golden-Age Hollywood classic like Casablanca. They all deserve to be counted among the best motion pictures in history.