Finding the sci-fi films that got missed
What "underrated" means on this page
Underrated here has a specific and slightly mechanical definition: films that score highly among the people who saw them, but that not many people have seen. The list takes a high score floor and then caps how many ratings a title may have, which is about as close as a database can get to the idea of a film that deserved a bigger audience.
That definition has one weakness worth knowing. It cannot distinguish a genuinely overlooked film from one with a small, self-selecting audience that was always going to love it — a niche title rated by its own enthusiasts looks identical, from the outside, to a neglected classic. Read the list as a set of recommendations from people who chose to watch these, which is useful, rather than as a verdict.
How to read this list
The order here is a consensus, not a verdict. It reflects how many people rated a title and how highly, which is a good measure of what reliably works for a wide audience and a poor measure of what is most ambitious or most original.
The practical way to use it is to treat the top of the list as the safe answer when you need one tonight, and to read further down when you have already seen the obvious titles and want something the consensus underrates.