2001: A Space Odyssey (1968)

The reason that this isn't #1 is quite simply that Ex Machina is more watchable and (superficially) easier to follow. In fact, I'd probably rank 2001 even lower if not for the scientific accuracy and the monumental impact on cinema. Remember that this was made before anyone had walked on the Moon! Yet space is silent, the spinning section of the ship creates artificial gravity exactly as it should, and everything moves the way physics says it would. Most space films made decades later can't say the same. And then there's HAL - polite, helpful, and utterly lethal. Every film AI since has been compared to HAL. Is it slow? Yes, painfully so at times. Does the ending make sense? I'm still not sure. But there's never been another film quite like it.