Not lesser known, but maybe under-appreciated. I rewatched “Oblivion” the other evening and enjoyed it. I perused reviews afterward and they all panned the movie for being too long and plodding at two hours, which makes sense I guess. But, honestly, after the subsequent decade of three- and four-hour blockbuster schlock, “Oblivion” now feels like a taut little thriller.

Cube if you consider it sci-fi. Trancers is campy fun. Moon of course. Sphere (the book is better though) is often overlooked. Dark City (make sure it's the version without the opening narration). eXistenZ. Gattaca. The Thirteenth Floor. Source Code. Paycheck is fun. The Jacket. 12 Monkeys. Pi. Equilibrium. Logan's Run. The Abyss

I'm going to say The Last Starfighter. It's quite old at this point, and it's derivative of a lot of other things, but it is a lot of fun.

Edge of Tomorrow since it hasn't been mentioned yet. Blew my mind the first time I watched it. I got sucked in and quickly suspended all disbelief. Then came the scene at the shack by the helicopter... I heard other people saw it coming but they totally got me with it. Such a pleasure to have my mind space tickled like that.

Event Horizon!

I quite enjoyed the French movie Oxygen from 2021, directed by Alexandre Aja. It's about a women waking up in a failing cryopod without any memory how she got there.

I'm a huge fan of the like microbudget (like 50k) psychological sci-fi film Coherence. They make the most out of their cast who semi-improvise much of the dialog and go the lo-fi approach to wonderful effect. It is easily found on several different streaming services, and is truly an underseen gem.

We have a soft spot for low-budget time-travel movies, like Primer, Time Crimes, and Triangle. Safety Not Guaranteed is also fun even though the Time Travel aspect isn't central to what's going on. The Endless is a must-see.

Koma - A Russian movie that (on the outset) sounds like an Inception knockoff but is good in its own right.

Life - Kind of a beat-by-beat "alien eats the crew" movie, but rather enjoyable.

Monsters - I found this one at the dollar tree of all places. It was shot with a skeleton crew (basically 5 people), but is well-acted, emotional, has a great score. Is still 100% sci-fi, though.

Clinic - A movie about a retirement community that holds a dark secret (also salvaged from the dollar tree 🤣). It's low-budget, but very well-acted, sets an anxious tone throughout so always feel on edge (in a good way).

Supervized - Honestly, reading the previous one of a retirement community reminded me of "Supervized," a unique take on the superhero genre. Played out like a comedy, but provides an interesting commentary on aging.

Otherlife - A New Zealand sci fi/suspense film about a dream technology that's being experimented with to keep people imprisoned (because 1 minute = 1 day, so 30 year sentence = 3 hours type of thing)

In the social media/'geek' sphere it is now overrated almost but when released and in the wider world fifth element was underrated. A big Bruce Willis action flick got almost no love at box office or video rental, it only really relied on word if mouth when on TV to become the cult classic it is today.

Not so much underrated but certainly overlooked -Primer. Also Predestination. Will check out Prospect.