Forbidden Planet was very much the template Gene Roddenberry used as a primary inspiration for Star Trek, though the C-57 Star Cruiser personnel looked a lot like a B-36 bomber crew more than the Enterprise crew.
One of my favorite classics is
Robinson Crusoe on Mars, well done and still watchable, even though the Mars science is outdated. The first half of the film depicts a marooned American astronaut's survival efforts on the Red Planet, the second half a first contact with intelligent alien life. Criterion restored the film some years ago, glad to say, and the soundtrack music by composer Van Cleave released on CD, too. Note that if you've ever watched it on broadcast TV, you've probably not seen the entire movie. It was edited, shortened for broadcast. The late actor Paul Mantee who portrayed astronaut Christopher Draper had some resemblance to real astronaut Scott Carpenter, and it's surely his finest performance on film. It was originally to be titled "Marooned" but another studio already had the rights to that name for another movie, that wasn't near as good. RCOM lore has it that if it had been financially successful, there would have been a sequel, "Christopher Columbus in Space", but that didn't happen. Memorable line:
"Mr. Echo, go to hell!" Mars Gravity Probe 1 fires thrusters
And, can't overlook Disney's 1954 version of
Twenty Thousand Leagues Under The Sea: a great cast and memorable performances by James Mason and Kirk Douglas, Nemo - my first anti-hero - travelled in a
nuclear-powered Nautilus, and those brief glimpses of the Nautilus' base at Vulcania (an electronic telescope dish!!!), what a great film!
New good sf films are, indeed, rare. I think Christopher Nolan's
Interstellar is the only one that comes to mind in past years.