"What if?" is the burning question our favorite sci-fi movies ask: What if Earth was invaded by aliens or giant spiders? What makes us human once we start bending the laws of genetics and robotics? And if we worked out really really hard, would we ever have Linda Hamilton's arms in "Terminator 2"?
Here are some of the best of the sci-fi genre now streaming on Netflix, including Chris Evans in "Snowpiercer," Bruce Willis in "The Fifth Element" and plenty of Godzilla and the crew of the USS Enterprise.
1. "Antiviral" (2012) NR
David Cronenberg's son, Brandon, makes his film debut with this gore-filled horror flick about a company who deals in viruses collected from celebrities since people want to be infected with the same diseases as the ultra-famous.
2. "Barbarella" (1968) PG
The cult film, starring Jane Fonda as the sexy space babe of the title, may be overlong, but it's an eye-popping must-see '60s flashback.
3. "Big Ass Spider!" (2013) PG-13
Greg Grunberg stars in this "Tremors"-like thriller about giant spiders rampaging across Los Angeles.
4. "The Brother From Another Planet" (1984) R
Joe Morton stars as an alien (in every sense of the word) navigating New York City in this cult favorite from director John Sayles.
5. "The Day the Earth Stood Still" (1951) G
Forget the remake with Keanu Reeves (sorry, Keanu). This Cold War classic about a peaceful alien who finds earthlings not very welcoming can't be improved upon.
6. "Errors of the Human Body" (2012) NR
A brilliant geneticist struggles to develop a cure for the disease that killed his son, while realizing he might have created something even deadlier.
7. "Europa Report" (2013) PG-13
Sharlto Copley ("District 9," "Elysium") stars in this found footage film set on Jupiter's moon Europa, where we may have just discovered alien life.
8. "eXistenZ" (1999) R
In this David Cronenberg thriller, you can actually enter your favorite video games. The designer of the addictive eXistenZ virtual reality game (Jennifer Jason Leigh) is targeted by assassins and playing the game is the only way to survive.
9. "The Fifth Element" (1997) PG-13
Grab your multipass and head to the year 2263, where Bruce Willis is a mouthy cabby and Milla Jovovich the scantily clad stranger who's the key to our salvation. Don't blink or you'll miss Luke Perry.
10. "Galaxy Quest" (1999) PG
This "Star Trek"-inspired sci-fi spoof, with Tim Allen as a Shatner-esque TV has-been, couldn't be more perfect, or more watchable. (Even if you've seen it a quintillion times.)
11. "Godzilla vs. Mothra" (1964) UR
The title says it all: Japan's two epic monster mutants go at it in a brisk 88 minutes of low-tech mayhem.
13. "Grabbers" (2012) NR
Tentacled creatures prey on an Irish fishing village in this sci-fi horror comedy.
14. "Invasion of the Body Snatchers" (1978) PG
While it doesn't have the noirish '50s paranoia of the original, this is by far the best of the many remakes of the sci-fi classic. Starring Donald Sutherland, Brooke Adams, and Jeff Goldblum, not to mention Leonard Nimoy!
15. "The Machine" (2013) R
British scientists create an artificial intelligence designed to help humankind, but things go very wrong when the military seizes it for its own, less lofty purposes.
16. "The Man from Planet X" (1951) NR
If you like your sci-fi campy and retro, check out this ultra low-budget entry from the man who directed the noir B-movie classic "Detour."
17. "Melancholia" (2011) R
Controversial Danish director Lars Von Trier ("Nymphomaniac") does sci-fi and the results are suitably nihilistic: It's literally the end of the world, after all!
18. "Metropolis" (1927) NR
This still breathtaking silent German Expressionist classic has influenced every science fiction film since. You can also stream the 1984 color-tinted version with music by Pat Benatar, Loverboy, and Freddie Mercury.
19. "Monsters" (2010) R
Before taking on "Godzilla" (2014), Gareth Edwards directed this film where the Mexican border is quarantined after an alien ship crash lands there. Now a journalist and a tourist venture into the "infected zone."
20. "Mr. Nobody" (2009) R
Jared Leto stars as Nemo Nobody, the last mortal on Earth who, at age 118, reviews his life and the different paths he might have taken.
21. "Sky Captain and the World of Tomorrow" (2004) PG
So it didn't set the box office on fire, this imaginative, artfully designed adventure is still worth a look. Plus, Angelina Jolie as an eyepatch-sporting aviatrix.
22. "Snowpiercer" (2013) R
Chris Evans is one of the wretched have-nots leading a rebellion against the "haves" on a supertrain that contains the only humans left alive after Earth freezes. Tilda Swinton is terrific as the upper class's condescending emissary.
23. "Star Trek Into Darkness" (2013) PG-13
Benedict Cumberbatch joins the "Star Trek" 'verse as "John Harrison," who's hellbent on revenge, like any intergalactic villain worth his salt.
24. "Star Trek IV: The Voyage Home" (1986) PG
In the fourth "Star Trek" film, the crew travels back to earth. Because whales.
25. "Star Trek VI: The Undiscovered Country" (1991) PG
The sixth film in the franchise -- in which Kirk and McCoy are charged with assassinating a high-ranking Klingon -- was the last time the entire original cast was together. Look for Christian Slater and model Iman in small roles.
26. "Stargate" (1994) PG-13
With a reboot in the works, now's as good a time as any to revisit the original film. It got horrible reviews when it was released (Roger Ebert famously gave it 1 out of 4 stars) but launched a devoted fanbase and several spinoff TV series.
27. "Strange Days" (1995) R
Set in the last days of 1999, Kathryn Bigelow's action thriller stars Ralph Fiennes as a sleazy dealer of high-tech merchandise and an especially fierce Angela Bassett as his bodyguard who try not to get killed before the new millennium.
28. "Terminator 2: Judgment Day" (1991) R
We never get tired of Robert Patrick's icy stare, Linda Hamilton being a badass, or Arnold Schwarzenegger saying "Hasta la vista."
29. "Total Recall" (1990) R
Arnold Schwarzenegger discovers he's really a spy with a mission to Mars in this action flick that may now be dated, but is still vastly superior to the recent remake.
30. "Upstream Color" (2013) NR
Critics called this trippy, abstract indie film from Shane Carruth ("Primer") "dazzling" and "transcendent," but also "perplexing."