Science Fiction

It's definitely not lesser known, but my favorite is The Expanse.

Farscape.

Look upward, and share the wonders I've seen.

Space: Above & Beyond. I thought it had some interesting ideas that were never given a chance to be fully explored.
Babylon 5. It's probably up there as #5 in your top 4, tbh.
Planet of the Apes. 1970s movies and TV series.

Definitely Farscape. A very weird but very good show. Ben Browder did a great job playing the lead role and it's a shame he hasn't done anything like it since.

I love Final Space :)

Galaxy Quest! I don't know if it counts since it's parody, but it's hilarious and well-made.

I will go for the oddball answer. The Outer Limits. The originals and the later ones. The episodic short story format works very well for me.

Fringe is an excellent show. It begins really episodic, like old school Outer Limits and early X Files. But by third season you're knee deep in a mind-bending larger story arc that absolutely rocks. The finale stands as one of my top 3 series closers. It expertly closes out the show with deep character resolution. And the show as a whole doesn't fall prey to the Lost Mystery Deficit. Mysteries are resolved, and there's great callbacks in final season to the mysteries of season one and two.

Furthermore, the cast is excellent. Joshua Jackson. John Noble pulling off Walter White levels of excellent acting and character change (you'll recognize him as Denethor from Lord of the Rings), and heck, Leonard Nemoy is in it.

If you love sci-fi, you can't go wrong with Fringe.

You could try Sliders, but the 90s corniness might turn you off.

As a kid, I was obsessed with the nickelodeon remake ofThe Tomorrow People but it doesn't stand up very well

Then there's Dark City and Gattaca for some more late 90s sci fi that I feel was bigger back then but no one really references anymore, but I think they are worth a view.

City of Lost Children is super weird but you can't deny the aesthetic is unique.

Winner of best movie with stupidest climax goes to Sunshine

If you count it as sci-fi, the HBO adaptation of "His Dark Materials" seems to have gotten basically zero attention in the US but was really quite excellent.

Also the original "The Prisoner." (the remake with Ian McKellen was meh)

Westworld season 1 is still one of the best seasons of science fiction television ever, in my opinion of course.

As a star Trek fan, The Orville. It takes a bit to get its footing, but season 2 and 3 are great. I hope it gets renewed for a 4th.

As for movies, Primer (2004) is one of my favorite. The first movie of its director (Shane Carruth), filmed with a ridiculously low budget of $20 000. It's hard science applied to time travel.

Be warned that this movie requires at least 2 or 3 viewings to really understand its story. Yes, it's that complex.

I loved Altered Carbon. Also, if you guys like anime, Psycho-Pass was really cool. If you like slow paced but atmospheric shows with a lot of connecting events and don’t mind watching a show in another language (German), then I would really recommend Dark.

I have a real soft spot for Raised by Wolves. It's so weird in all the right ways.

Akira.

Defiance was amazing, it's clear SciFi was spending a bunch of money on it, which ended up getting it killed.

Red Dwarf.
It's goofy. It's campy. It's sometimes terrible.
But it grows on you and by the time you are done through season 2 you love the show and only want more. And oh yes there is more, much more.

no love for 12 monkeys tv series? great series

Andromeda holds a place in my heart that it probably doesn't really deserve. Definitely full of cheese, and the character of Dylan Hunt is awful.

I'll probably still always love it, mainly because it came out when I was a kid.

Maybe a bit of recency bias creeping in here but the first season of Severance was spectacularly good. Really hope they can keep that quality up.

Given the amount of people I recommend it to who have never heard of it I think this definitely counts as "lesser-known".

It's not really less-prestigious, and I am not really a sci-fi fan, but Contact.

I think I'm the only person to ever watch all of Andromeda. It was not my favourite show, but there was something comforting whenever i was watching it. Maybe it just reminded me of the old Hercules, but in space.

The Adventures of Brisco County, Jr. At the time, I couldn't understand why everybody preferred that boring FBI monster show with the monotone lead actor.

No, Firefly doesn’t count as lesser-known.

awww :(

Less Prestigious would be Flash Gordon; utterly camp and very fun. DIVE!

Fringe was very cool.

Off the top of my head, Fringe, but that's not really lesser known. On more thought, Earth: Final Conflict and Primeval.

Dark Matter was amazing. Farscape was almost perfect, in my opinion. Finally, Firefly was astounding in its short time.

All are worth checking out.

In the spirit of the question (not picking the most common ones), I'd say Sanctuary was good. I think it was very (very...) low budget (everything is green screen) but the stories were great. There are a lot of fantasy elements but I think it's very scifi.

Big Hero 6. Seriously, I love the franchise.

Dunno how lesser-known were Dark Matter and Killjoys but these are probably my favorite non-Star, non-Firefly, non-Expanse shows. I did also like S1 of Altered Carbon and Raised by Wolves

If you haven't seen it yet, check out the movie Coherence (2013)! It's one of my favorite sci-fi movies. The actors were taken aside and given certain direction but were never given a full script, so every time you see them arguing or trying to figure out what's happening or surprised by something, it's all genuine.

Here's the synopsis but don't read anything else about it before you watch: [Synopsis: Strange things begin to happen when a group of friends gather for a dinner party on an evening when a comet is passing overhead.]

It's free if you already have Amazon Prime. A fantastic sci-fi puzzle to solve (similar to Primer in that way but very much its own thing).

As my username suggests- I love 'Lexx'.

It's beautifully sleezy sci-fi fantasy and not nearly enough people know about it. I caught it on Netflix about 10 years ago but I think you can watch it on youtube now free with commercials.

Highly recommend to any fans of sci-fi, but especially if you loved stuff like Farscape and Red Dwarf.

Also shout out to 'Avenue 5'. Hilariously dark sci-fi comedy that HBO criminally underpromoted. Also 'Other Space'.