Before Sunrise
Probably the most authentic depiction I've seen of two people recognizing an instant connection with one another. The whole movie is just these two adults talking and getting to know each other, no drama, no misunderstandings, none of the things that I dislike about romance stories.
"If there's any kind of magic in this world, it must be in the attempt of understanding someone, sharing something. I know. It's almost impossible to succeed. But... who cares, really? The answer must be in the attempt."