I really feel like some of the best remembered movies out there, the game changers, feature really incredible dialogue.

I was thinking about Ep IV, and how there are all these little awesome one-line keys to character scattered throughout the script. Luke straight up tells you that he's bored or curious enough to go looking at exactly the sort of people you don't want to bother; Tarkin admits he'd rather massacre civilians unrelated to his war as long as it's an effective terror tactic in the same scene that Leia does the most heartfelt resistance leader speech since Casablanca.

Going beyond that, I was thinking about how the initial exchange between Deckard and Rachel completely nails the rabid fire conversation in film noir. The Germans in Raiders of the Lost Ark get this somewhat formal, stilted language which definitely conveys threat and tells you they're not as slangy and informal as our American heroes. The Godfather's characters definitely have speech patterns that give you a clue of who they are, and what their world is like, similarly because Michael is such a contrast in how he speaks that his eventual embrace of his father's position is huge.

I bet there are a whole batch of other examples where really subtle language use are what really pushes a movie.