Just to add on to some things people have already said:
The fact that this movie was made in 1969 adds to its amazing quality. I mean, we're talking a whole 8 years before Star wars. As a matter of fact, I think the dude who did all the space sequences went on to work on Star Wars based off of his work on this movie. It's insane that you could watch this movie today and the special effects look great. There's movies from the 70s, 80s, and 90s that pale in comparison to this one.
Also, the music used in this movie has become so re-used and cliche at this point in pop culture that the audience watching it in a modern context could easily forget that this movie was the FIRST to use those symphonies. That's how iconic it is.
Look at the set design (like dude said before, u have to be a cinephile to appreciate the subtle things)....like the interior of the ship Dave is on. It's I mean a lot of this stuff is made up/straight out of Kubrick's imagination. That's some truly crazy shyt. Kubrick was really a dude who understood shot composition. You could take a still of any scene from this movie and make a poster out of it.
the best post in this thread..
he was genius and a very hard man to work with..he brought out the best of his workers.