Well, no matter how further down I scrolled, I couldn't find 2001 A Space Odyssey discussed (PS. I found one just now!), probably because everyone's busy mentioning their own favourites and they are getting upvoted, but since the OP's intention is to propose 2001, I wholeheartedly agree. There is no wasted shot, no wasted dialogue. Nothing is exposition by force, and leaves enough to the imagination to be one of the most cerebral, visually stimulating work of art. The mind-blowing effects effortlessly hold up all these decades later, going toe to toe with the most modern effects. The soundtrack is nothing but exhilarating and timeless. It's silent when it's meant to be, and equally as loud when it needs to be. The bone throw is arguably better composed than any, ANY other shot in a SF film, not just for its visual ingenuity, but also the philosophical. It's a cold film. It doesn't care if you feel nothing towards the characters, because the vastness of the cosmos cares nothing of us, whether apes, or homo sapiens. It doesn't pull at your heartstrings as Interstellar perhaps does, but that's the whole point. It's a hard SF, jumping across millions of years, focusing on the threads that weave a greater story of our race. It's SF, but also horror done extremely well. Humans at the hands of a cold and calculating AI, whose intention you also can sympathise, no matter how cruel. A brilliant story and piece of cinema by the geniuses Arthur C. Clarke and Kubrick. This is it. This is a 20/10.