I only have 4 off the top of my head lol. The rest (basically Star Trek, Quantum Leap, Twilight Zone) are TV shows.
TRON
This movie was made at the right time: just after they moved past utility and into entertainment but before they became complex enough to do everything for us. Ironically, a certain character poses that scenario even as TRON was banned from Special Effects awards at the Oscars, because "using computers was cheating". The Matrix does a similar thing with the relationship between man and machine but TRON is more on the nose with its computer allegories, thus it's more comprehensible.
The MCP began as a small chess program and will end small, says the Tower Guardian. I love how MCP's functional existence exactly matches its moral narrative, just as the Programs represent the ideals and purpose of their Users. The User-Program dichotomy even extends to religious thought and that communication between the User and a manifestation of their spirit is profound.
I also like that Kevin Flynn is content with just getting his games back and that the story is barely about the MCP trying to take over the world. That's kinda funny, but kinda weird when they took him in the opposite direction in Legacy. Flynn is right that he stumbled onto world-changing concepts, but the story is somehow just less interesting.
TRON is incredibly forward-thinking in its real-life production and in-film themes. It's incredibly tragic Disney doesn't know what to do with it.
Star Trek VI: The Undiscovered Country
After 20+ years on TV and movies, the Enterprise crew is forced to confront that they are set in a lifestyle and worldview that is no longer conducive to peace.
This movie is a huge lesson about hate not being as it seems. While the conflict presents itself as the Federation vs. Klingons, it turns out there are factions on every side that don't want to see peace between the two.
Metropolis
The society is broken down into a machine-like class system, and like my other favorite scifi and fantasy stories it requires a force beyond what neither the head or hands (as the film describes) can grasp on their own. The society can only work if there is a heart that understands the needs of both.
Also I like it for its various influences on Superman.
E.T. the Extra-Terrestrial
Spielberg's story of an imaginary friend framed as a realistically portrayed alien visitor.
I don't think it has a major scifi theme except perhaps that humans can be more foreign than a friendly alien.
...okay enough rambling