How I Wish, How I Wish You Were Here...

Solyaris (Solaris)(1972)

Directed by Andrei Tarkovsky

"We don't want new worlds, we only want to expand Earth endlessly. We don't want anything new. We just want a mirror."

One the best movies ever. EVER.
It is very slow though, and though I enjoyed the remake, this rises above the source material and becomes something more, you could re-tell the story, but you could never remake this movie.
A psychologist is sent to investigate a rash of strange hallucinations plaguing a group of cosmonauts orbiting a planet covered entirely by an ocean.
The cosmonauts are seeing those they left behind on earth, the dead and those they wish were with them.
They believe the planet is causing these people to appear, the people themselves contain only the memories of those who remember them and slowly become aware of their artificiality.
It's truly haunting and emotionally harrowing, while not sacrificing an inch of it's speculative curiosity, a rarity in science fiction, and films in general. And the 15 minute, Tokyo freeway scene, and the final scene as the camera zooms out are two of the best Ive ever seen anywhere.
Solaris is to inner space and internal experience what Stanley Kubrick's "2001: A Space Odyssey" is to outer space and man's external environment.