I saw this film/tv show (tend to think film) when I was a kid and have been trying to find out what it is since then, it's driving me insane! It's definitely a 60s/70s film that I must have viewed sometime around 1980, give or take 3 or 4 years.
The only scene I remember is one where the main male character is with two or three other people and he looks up at a distant planet in the sky (could possibly have been on a monitor/tv screen) and says something like "that planet up there...it's Earth, isn't it?". The main character thought that he was already on Earth, and the others were letting him believe this. He has slowly realised that he is being fooled. Perhaps he was a human anstronaut..travelled through space...landed on what he thought was Earth, but apparantly not... Very paranoid and sinister.
This is not 'The Martian Chronicles' with Rock Hudson, nor the later Ray Bradbury Theatre stuff. I'm sure it had a vibe/look similar to 'The Invaders' with Roy Thinnes. It could have starred someone like John Saxon or Karl Malden.