sorry, i had to go and listen to "everyone says i love you" on youtube.
yes, exactly, excellent example from casablanca ! i think the dialogue is maybe the biggest reason we can watch these films over and over without ever getting tired of them. the dialogue is so witty, so brilliant, so subtle, it stays fresh, and each time you notice new details.
we had a dialogue writer in france, Michel Audiard, he was later (mostly active in the 60's) but in a way he belongs to the same tradition ; he was like a silversmith of words. his dialogues are unbelievable ; it seems impossible that one person could write so much sheer brilliance.