Which of these is the greatest sci-fi film?

And to clarify, not necessarily which you think is the best film, but which is the greatest as a piece of science fiction, bearing in mind when it was made.
Please bear in mind directorial imagination, innovation and influence, as well as its insightfulness into the future and any comment it makes on humanity/society.

For Blade Runner, I had the Director's cut in mind, but up to you guys.

@Yoda?! has kindly added The Andromeda Strain. Many thanks.

I am increasingly loving Alphaville.
Unlike almost any other film, the more times I watch it the more I appreciate it as a work of genius and masterpiece.
I think it is Godard's greatest work.

I like that instead of just asking which is our favorites, you've asked more detailed and thought provoking questions, which makes for a better thread and conversation.
My thoughts on the four sci-fi films in regards to your query:

Alphaville 1965...A cool French new wave film. Not much in hard sci-fi but big on societal commentary which was relevant to what was going on in the world and in French politics at the time. There are many unconventional story telling methods used to further the narrative, coupled with some really innovative camera work like the direct edit 'I came to give you a light'. I don't know how much Alphaville influenced other film makers, some of course, but I'd say the other three sci fi films you listed had more influence on future sci fi films. Though the filming style of Godard did influence future films.

2001 A Space Odyssey 1968...When I think of Kubrick and 2001 I think of a perfectionist, someone who technically and visually could make their sci fi film look utterly real. Kubrick makes the space voyage part of the film seem slow, which then gives us the feeling of space travel as if we were along for the journey.2001 is the most iconic of the sci fis listed.

Alien 1979...I'm a big fan of Alien, I say that so it doesn't sound like I'm knocking the film, I'm not...but I'd say Alien is like this really cool extreme carnival ride that thrills everyone, fun as hell but not that deep. The biggest aspect of Ridley's Alien is the set design done by H. R. Giger. The look and Ridley's atmosphere of Alien is still being copied today.

Blade Runner 1982...I might be bias in my opinion of Blade Runner but I'd say this one is the winner in regards to "directorial imagination, innovation and influence, as well as its insightfulness into the future and any comment it makes on humanity/society"...Ridley really shines with his world building/set design skills. If I remember correctly Ridley started out as a set designer. Blade Runner takes alot of the real world and stretches it into a believable future that's not so rosy. It makes one helluva a comment on how society treats people viewed as 'less important'. Oh.. Deckard was a human, not a replicant.

I like a lot of what you say. Interesting.

I would just say a little about Alphaville though.
Alphaville is set in the future (I think the 1980s), which seems to have been something of a first or at least very unusual then.
It has a really strong sci-fi element. It's really sci-fi meets espionage. Alphaville is controlled by a computer (possibly the first to appear on the big screen), and a big theme of the movie is technology taking over humanity. There is actually a line of dialogue to this effect.
I think it was hugely influential on later sci-fi movies plus probably the likes of Black Mirror because it mixes very contemporary looking France with the futuristic.
Also because of its slightly farcical style and largely impressionist fight scenes etc, its influence is very evident on stuff like Naked Gun and even possibly the Batman tv series, which started the following year. As well as this is has a real sense of poetic story telling about the romantic angle.

I also have no idea where on earth you get the idea from that Deckard is human!!!!!

Thanks for your insightful comments and also your kind feedback.

I didn't know Alphaville was run by a giant computer or that technology was taking over. I only seen it once and hardly remember it but I bet the omnipresent computer/technology controlling Alphaville was a metaphor for French politics or world society at the time.

I think that's a movie that really needs a 2nd or even 3rd viewing to really appreciate it.

I am not a fan of Space Odyssey or Alphaville. Alien followed by Blade Runner.

I really think it is. I was thinking the same thing earlier. In fact my thread was initially going to be about films that need more than one viewing! I find that I grow into it the more I watch it. It's also one that you have to stick with for a while before it absorbs you into its world.

Another sci-fi film from this 'period' that I really like by the way is The Andromeda Strain, but that's more about the tension and the visuals than it is the innovation, influence, intelligence/messaging etc (although it does score pretty well I reckon on futurism).
I reckon visually it arguably gives 2001 a run for its money.
Also I guess it's more of a disaster movie crossover.

2001: A Space Odyssey is my favorite film regardless of genre
An easy vote for me

In my opinion, only three if those I like Blade Runner, Alien and 2001.

This is the kind of thread I like, you make a lot of good threads and somebody has to make them or we don't have anything to talk about. BTW which version of Blade Runner are you familiar with? It dawned on me that you might be familiar with the Blade Runner The Final Cut, which of course is different than the original.

Good point. It's actually the director's cut that I had in mind, which I think is actually 1992. Perhaps I should clarify that in the OP.
Up to people I suppose though based on their own preferred version of the filme

Most people are familiar with the director's cut of Blade Runner, I kinda hate that as I dislike original art being modified at a later date...unless it's something like syncing the sound better or removing the lines from the spinner cop car. But I dislike that Riddley, reshoot a scene, removed other scenes and tries to rewrite the ending to make Deckard look like a replicate. In the original theatrical release he clearly was a human.

Interesting.
If I've seen the original cut it was a long time ago. I'll try to check it out. Thanks for the heads up.

I'm really surprised at one of the co leaders. It would probably have been last for me on the criteria suggested!
Interesting though all the same.