Superior to The Day the Earth Stood Still
When we are talking about science fiction movies dealing with aliens and/or Space travels, there were two big movies in the 50s: The Day the Earth Stood Still and Forbidden Planet. I have never understood why The Day the Earth Stood Still was so big. It's not that different from Ed Wood's Plan 9 from Outer Space. I'm not sure if there was any interesting movies about the subject before Forbidden Planet (it could be, but if so, they are not well known). A Trip to the Moon was good, but this surreal short is not exactly a feature.
(And in the 60s, there was 2001: A Space Odyssey.)