Not the best, but your favourite

Probably CE3K. I really don't know how many times I've watched that.

T2

Or Alien....Ripley in her smalls when you're 15....

Edit, double post - forum aliens in the works

Does The Matrix count? I’m not a huge sci-fi guy, but I love that film.

Starship Troopers. Would you like to know more?

I'm not a huge sci-fi fan, I find many sci-fi films shallow and overrated. I hate it when they pretend their wafer thin plots are deep, meaningful philosophies. The matrix is probably the worst for this, but I feel the same about some of the most highly regarded movies. I'm not going to mention them as it usually makes people unaccountably angry.

Having said that there are many that I have really enjoyed ever since I was tiny - The Day the Earth Stood Still, Forbidden Planet, The Time Machine, Logan's Run, Westworld.

A bit more recently I like Back to the Future, Robocop, Twelve Monkeys. does Being John Malkovich count?

I haven't seen anything I've really enjoyed for years - I thought Minority Report was good, but that was two decades ago.

Avengers Endgame: but is that Sci-Fi? If not 2001.

I can never resist "The Chronicles Of Riddick". It's extremely daft but I love the Necromonger design aesthetic and stuff keeps happening at a pretty decent pace.

Or Alien….Ripley in her smalls when you’re 15….

I saw Alien/Aliens back to back at the NMFP&T many years ago, before the franchise disappeared up its own arse. I remember noticing at the time that she goes into hypersleep at the end of Alien and is then rescued by the salvage team in Aliens wearing completely different underwear. It always amazes me what trivial nonsense my idiot brain remembers from what must be 40-odd years ago!

Solaris. The Tarkovsky one.

[i]she goes into hypersleep at the end of Alien and is then rescued by the salvage team in Aliens wearing completely different underwear.[/i] - possibly unrelated but I saw a program about male bats waking from hibernation to have sex with hibernating female bats. The female never wakes or is even aware of this but wakes up pregnant. Possibly something similar happens in hypersleep?

[i]she goes into hypersleep at the end of Alien and is then rescued by the salvage team in Aliens wearing completely different underwear.[/i] - I am not surprised the salvage team in Aliens were wearing completely different underwear, fashion change, even in deep space

possibly unrelated but I saw a program about male bats waking from hibernation to have sex with hibernating female bats. The female never wakes or is even aware of this but wakes up pregnant. Possibly something similar happens in hypersleep?

Well, that's taken a bit of a dark turn.

I am not surprised the salvage team in Aliens were wearing completely different underwear

I accept that I could have punctuated that better...

Aliens ...wearing ...underwear....

Different genre surely...

I don't have favourites of any kind. I dislike and reject the concept of favourites, it's restricting.

But I really liked the film Silent Running.

Batteries not included...

I don’t have favourites of any kind. I dislike and reject the concept of favourites, it’s restricting.

But I really liked the film Silent Running.

Don't worry, we won't tell all the other films. All those ones you like indistinguishably...

My favourite? Blade Runner.

It's also possibly the best though...

HMs to...

Starship Troopers

Star Wars

Silent Running

The Fifth Element

The Martian

Twelve Monkeys

Hardware

Probably Bladerunner. Especially because it gets occasional cinema releases- I've seen it a bunch of times this way and it always blows me away, I forget how good it is (even though I remember that I've previously forgotten how good it is, it's still better than I expect).

I do love Aliens though. And Mad Max 2

(@flyingox, what a gorgeous film that is...)

Dark Star.

Bladerunner is my favourite, but it's also the best so I guess I don't get a vote.

Tough call. I really enjoy Inception.

Is Predator sci-fi enough?

Far too many to choose from but my favourite which they have never made a sequel to but should have is....

District 9

The Final Countdown (1980)

Aircraft/aircraft carrier porn in a thunderstorm. USS Nimitz goes back in time to the day before Pearl Harbour; F14 Tomcat v "Mitsubishi Zero" anyone?

Predator, I'm saying it's action sci fi so acceptable. It is a superb film, underrated imo but pretty much perfect on every level

District 9, good call.

Invasion of the body snatchers - the original 1956 version.

Gravity and Interstellar are two of my favourites.

The Final Countdown (1980)

Aircraft/aircraft carrier porn in a thunderstorm. USS Nimitz goes back in time to the day before Pearl Harbour; F14 Tomcat v “Mitsubishi Zero” anyone?

This was on the shelves of the local video place when I was ten years old. The concept intrigued me but I never watched it until I found it on a dodgy DVD stall in Jakarta. Sadly, rubbish film.

The Martian

Terminator 2 for the generic answer

The Fifth Element for a less obvious answer

And I like Star Wars which hasn’t had a mention yet? That’s how uncool i am

[i]And I like Star Wars which hasn’t had a mention yet? That’s how uncool i am[/i] - Never seen it, worth watching?

Back to the Future.

If we're only talking space-based sci fi

Star Trek: First Contact

Prey was genuinely better than Predator.

Anyway the answer is obviously Galaxy Quest

Never give up, never surrender 

If you like Ms Weaver in Aliens you'll love Galaxy Quest

Interstellar

Contentious opinion: I prefer The Terminator to T2, and Aliens over Alien.

Trying to think of films not already mentioned.  Depending on your definition of sci-fi:

Cube

Cypher

Pitch Black

Harrison Bergeron

Titan AE

I don't think Aliens over Alien is all that contentious. Though I'd expect the venn diagram of Aliens preferers to overlap more strongly with T2 preferers.

I couldn’t pick just one, it would have to be a top five.

Star Wars as a trilogy - it’s one story.

The Martian,

Interstellar,

The Fifth Element,

Star Trek First Contact or Wrath of Khan.

Oh I forgot about Prey, I really enjoyed that. When I first watched it I didn't even know it was a Predator film.

I once watched Blade Runner on a big screen outdoors in Battersea Park. There was low misty cloud that evening with jets lining up for Heathrow flying directly overhead with their lights shining through the murk. At one point during one of those shots of the city you couldn't tell where the edge of the screen was.

Favourite, I'm going with Dark Star.

The Martian

Great film. To be just a little bit controversial, is it really sci-fi? It mostly involves existing technology.

At the moment it's still science fiction for humans to be on Mars so for me it's still sci-fi until they step foot on Mars.

It's fiction and at one point he's literally 'sciencing the shit' out of things. Probably allowed.