Some underrated films I would recommend:
THE ANDROMEDA STRAIN (original) - like THE MARTIAN, real “science” science fiction - the research team has to solve a problem, using real science and scientific methods, or the world dies.
THE MAN WHO FELL TO EARTH (original) - Completely bizarre and oblique but amazing. Probably a good vision if what would actually happen if a hypertechnical alien came to our planet. Plays with a lot of genre conventions.
THE BED-SITTING ROOM -Not many have seen this. Members of Britain’s premiere comedy teams (The Goon Show, Cook & Moore) in a comedic post-apocalypse Britain where the government bombs any remaining structures to deny them to the enemy and people spontaneously mutate into bed-sitting rooms.
LOS ANGELES AD 2017 - a made-for-TV movie that was part of the early 1970s TV series THE NAME OF THE GAME but was essentially a stand-alone movie, one of the first projects directed by Spielberg. A publishing magnate falls asleep at a roadside rest stop and wakes up in an L.A. that was devastated by ecological collapse.
WESTWORLD - Just rewatched this yesterday. Tight, lean film well directed and written by Michael Crichton. Yul Brynner was able to make a robot interesting as a character, First use of computer graphics in a major movie, very influential on films like THE TERMINATOR, every stalker film with an unkillable enemy, and THE CABIN IN THE WOODS. What did Crichton have against amusement parks?
THREADS - a very realistic depiction of a nuclear attack on Britain. Amazingly depressing ending. See also THE WAR GAME by Peter Watkins for a documentary-style look at what a nuclear strike on Britain would be like.
1984 - The version with John Hurt, actually released in 1984. The best, most accurate adaptation of Orwell’s novel.
FANTASTIC PLANET - an animated French production, with a bizarre alien ecology well depicted.
PRIVILEGE - Another Peter Watkins film about media manipulation of pop culture. A young pop star is used by a near-future British government to influence the young.
VIDEODROME - Cronenberg’s view of how we let media input influence and ultimately control us.
SECONDS - John Frankenheimer’s very disturbing look at a man in a mid-life crisis who contracts with a shadowy corporation to fake his death and give him (after surgery) a new hedonistic life. The best performance Rock Hudson ever did. Will Geer is memorably creepy as the corporation head.
THE LATHE OF HEAVEN (original) A PBS adaptation of Ursula K. Leguin’s novel, low budget but an excellent cast and very memorable.
Z.P.G. - Oliver Reed in a future dystopia which restricts the birth of children as a population control measure. See also THE LAST CHILD, a made for TV movie with a young couple in a similar, China-like future who has to flee to Canada to protect their child with an implacable Ed Asner in hot pursuit.
PUNISHMENT PARK - Peter Watkins, yet again, as a documentary crew follows a group of SoCal radicals who are given the chance to flee across the Mojave desert to reach a flag while pursued by police and National Guardsmen, in order to receive parole for their crimes. I don’t share Watkins’ political stance but its still a damn impressive movie.
ROBINSON CRUSOE ON MARS - A classic from my youth. The science is passe but the sense of wonder is still there.
ROLLERBALL (1975 original) James Caan and John Houseman are excellent in a view of how sports can be used to control and divert the population, in a world where the nation states have vanished and corporations have taken their place.