Movies have long been at the forefront of space exploration, whether it's with alien encounters, time travel or just toying with way-cool technology.

So when we sat down to compile our list of the best sci-fi movies of all time, we looked all the way back to the classics ('Forbidden Planet'), to the movies that defined their times ('2001: Space Odessey') and our childhoods ('Star Wars').

It was one small step for Moviefone, one giant leap for movie lovers. Join us as we count down the 25 best sci-fi films of all time.
25. 'Close Encounters of the Third Kind' (1977)Steven Spielberg's first nomination for Best Director finds him in truly terrific form examining all the urban legends of visiting aliens and flying saucers, grounded in the story of the everyman who longs for something outside of his suburban life. This one only gets better with age, and mashed potatoes will never look the same.

24. 'Star Trek II: Wrath of Khan' (1982)
Ricardo Montalban reprises his role from a 1967 episode of the TV series, 'Space Seed,' as Khan Noonien Singh, exiled by Kirk and now back for his revenge. Too bad the rest of the film series never came close to being as good as this tale of vengeance that ends with the death of (spoiler alert!) Spock. Will the JJ Abrams prequel deliver a film that can live up to it? No pressure, but Trekkers can only hope.

23. 'It Came From Outer Space' (1953)
A young astronomer watches a meteor crash that turns out to be a spaceship smashing into the sand. Folks who went to gawk at the spectacle returned oddly transformed. This eerie sci-fi flick was the first to introduce shape-shifting aliens as a plot device and the Arizona desert as a home base for UFOs. The 3-D movie won a Golden Globe for Most Promising Newcomer Barbara Rush.

22. 'Galaxy Quest' (1999)
By far one of the best sci-fi sendups ever. Tim Allen stars as a Captain Kirk-esque actor expected to save real aliens from their galactic fate (adding to the fun is the echoes of similarity to his Buzz Lightyear character). With funny performances by Sigourney Weaver, Tony Shalhoub (Monk) and the always sublime Alan Rickman. Never give up, never surrender.

21. 'Robocop' (1987)
Who knew Red (Kurtwood Smith) from 'That 70's Show' was such a badass? But the real star of this tale is Peter Weller as Murphy, a great cop made better -- with a little tinkering and some spare parts. Director Paul Verhoeven's tale of a crime-ridden future Detroit is sci-fi at its most cynical ... and entertaining. Part man. Part machine. All good.

20. 'Tron' (1982)
Before cell phones and iPods and computers you could slip in your bag, PCs were the size of big-screen TVs with a fraction of the power of your kid's laptop. This film's hero was a hacker (Jeff Bridges) who gets sucked into his machine to do battle with a main frame. It's like 'Spartacus' for early computer geeks. 'Tron' mixed live action and animation and had some cool effects for its time, even if we didn't know what the heck RAM was. It also won an Oscar for Best Costume Design. Byte on that.

19. '12 Monkeys' (1995)
Terry Gilliam's mind-bending film was inspired by Chris Marker's 1962 short, 'La Jetee,' which brilliantly captured a dark dystopian future world that falls back unto itself in a twisted tale of time travel and lost hopes. In a post-apocalyptic future a few survivors live underground to avoid a deadly virus, while Bruce Willis is sent back in time to try and save the future from a crazy Brad Pitt and his cohorts. Best line: "There's no right, there's no wrong, there's only popular opinion."

18. 'Soylent Green' (1973)
Beware of the Soylent Green wafers. Soylent Green is...well, we don't want to give away the secret ingredient if you don't already know, but let's just say some of us still avoid eating soy products to this day. Charlton Heston plays a New York cop, circa 2022, trying to beat the heat and synthetic foods. Edward G. Robinson, who was almost totally deaf during the production, was Heston's roommate who helps his pal figure out what the heck they're really eating.

17. 'Brazil' (1985)
A box office bomb that was heaped with praise by critics at the time of its release, even winning the Best Picture honors at the Los Angeles Film Critics Awards, Terry Gilliam's trippy flick has aged well ... unlike Katherine Helmond's character, who goes to ridiculous lengths to remain youthful. Smart, dream-like, twisted, constantly entertaining and visually ravishing -- this take on the Orwellian nightmares of a humble office drone continues to amaze audiences. Just goes to show you that critics can be right sometimes. Really.

16. '2001: Space Odessey' (1968)
"Open the pod bay doors, HAL." "I'm sorry, Dave. I'm afraid I can't do that." This Oscar winner for special effects garnered Stanley Kubrick the second of his four failed Best Director nominations. The imagery is unbelievable and it does what all science-fiction films should do: inspires us to believe in other worlds and other civilizations that are out there. Somewhere.

15. 'Planet of the Apes' (1968)
A classic movie by Franklin J. Schaffner that launched a franchise that has yet to die. It spawned four sequels, one overblown remake by Tim Burton, a television series and animated series that obsessed every prepubescent boy in the early '70s. The ending is beyond iconic, and the dialogue endlessly quotable: "Take your stinkin' paws off me, you damned dirty ape!" Charlton Heston has never been hipper.

14. 'Invasion of the Body Snatchers' (1978)
Some are partial to Don Siegel's 1956 original, but that McCarthy-era sci-fi shocker was once thought to be too disturbing for the masses, so the ending was softened. Not in this version, folks. Directed by Philip Kaufman and set in San Francisco this time around -- this horror/alien-invasion gem starred Donald Sutherland and concluded on a note of terror. Now if we could only do something about that scream ...

13. 'E.T.' (1982)
This little dude just wanted to go home. Steven Spielberg's film that dethroned 'Star Wars' as the box office champ (until a certain sinking ship came along 15 years later) has transformed from a cultural phenomena into a "classic kid's tale." We beg to differ. While the heroes remain children and a rubberized midget, the straightforward storytelling and the ability to tug at the heart string made this the movie to see in 1982 and a long time after.

12. 'Metropolis' (1927)
This Fritz Lang classic set the bar for all sci-fi films to follow. The first really great sci-fi flick still packs them into revival theaters if you're lucky enough to catch it on a big screen. "Lost" footage was recently discovered, so expect a brand new revival, quickly on the heels of the most recent "complete restoration." And yes, the robot/ android/whatever creature, Maria, influenced the design of a character you might have heard of: C3-PO in a little flick called 'Star Wars.'

AFP / Getty Images11. 'Terminator' (1984)
"I'll be back." Who but Arnold Schwarzenegger could deliver that line so perfectly? With director James Cameron behind the helm, this time-travel tale raised the bar for cyborgs everywhere. Relentless and unstoppable, 'The Terminator' won over audiences with its action-packed pacing, special effects and one-liners. It probably helped Schwarzenegger get elected in California too.

10. 'Forbidden Planet' (1956)
The film debut of Robby the Robot alone makes this one for the history books. This sci-fi classic was loosely based on Shakespeare's 'The Tempest' and was Gene Roddenberry's inspiration for 'Star Trek.' A young Leslie Nielson stars as Captain J. J. Adams in the out-of-this-world tale. Surely you can't be serious? We are, and stop calling him Shirley.

9. 'Alien' (1979)
Horror meets sci-fi in this hit film that kept audiences screaming long after the lights had faded on the alien menace. Unfortunately for us, the acid-dripping beeyotch would return about 40 more times. Still, the original film and its gut-wrenching scenes gave us one great sequel and introduced us to the hottest action babe to grace space, Sigourney Weaver's Ripley.

8. 'The Thing' (1982)
1982 was a great year for science fiction movies ('Blade Runner,''E.T.,''Star Trek II') and this John Carpenter classic is no exception. Starring a shaggy Kurt Russell as helicopter pilot R. J. MacReady, this scary sci-fi thriller about a shape-shifter alien set in an Antarctic research station is a gory, paranoid mess of an adventure. Some critics even recommended bringing barf bags to screenings. Now don't lose your head, but the only thing we'd bring to this cult classic is a flamethrower -- and don't forget to torch it!

7. 'Terminator 2: Judgement Day' (1991)
Arnold Schwarzenegger riding a hog with a shotgun -- makes Sarah Palin look like an amateur. 'T2: Judgement Day' is even better than the original with a bigger budget, more effects and an all new T-1000 played by 'X-Files' stand-in Robert Patrick. Ah-nold gets to play the good guy this time around and the best scene comes at the end with its big thumbs up by the Terminator. 'T2' also snagged four Oscars -- not too shabby.

6. 'The Matrix' (1999)
This is the one. Really it is ... but the sequels? Not so much. This film about a hacker, a sexy babe, a bad ass named Morpheus, and a villain called Agent Smith, is an action-packed virtual roller coaster ride created by the Brothers Wachowski. Keanu Reeves, stars as the savior but Carrie-Anne Moss heats up the screen here. Take the red pill, sit back, relax and get ready for some fantastic action.

5. 'The Day the Earth Stood Still' (1951)
Director Robert Wise may have won Oscars for directing 'West Side Story' and 'The Sound of Music,' but for us, his real contribution to movie history is this simple, pared-down look at the end-of-the-world-scenario featuring a cool alien menace, the threat of annihilation, a call for nuclear disarmament at the height of the Atomic Age and one of the smartest and most entertaining sci-fi movies ever filmed, Yes, we are on the verge of the big mega-bucks remake, but can they really hope to match the sense of awe and fear that originally followed these famous words: "Klaatu barada nikto"?

4. 'Star Wars - A New Hope' (1977)
Despite what came after, including too much tweaking on George Lucas' part, this one remains the box office wonder and crowd-pleaser that brings smiles to fanboys (and fangirls) everywhere. Lucas looked to Akira Kurosawa's'The Hidden Fortress' (1958) for the basic source material, and his riffs on 1930s movie serials, from the opening title crawl to the iconic scene where Luke and Leia swing across a gaping chasm, delighted movie audiences the world over. Ten Oscar nominations, including Best Picture, Best Director and Best Supporting Actor for the legendary Alec Guinness.

3. 'Aliens' (1986)
This sci-fi sequel is even scarier than the original and like its leading lady, Sigourney Weaver, more pumped up and ready to kick more alien ass. This terrific tale takes place 50 years later, when lone survivor Ripley and her cat wake up and are finally rescued, only to be sent back to another nightmare. At least this time around Ripley has a bunch of space Marines to use as bait. James Cameron directed, and it won Oscars for Best Sound and Visual Effects.

2. 'Star Wars: The Empire Strikes Back' (1980)
Also known as 'Star Wars: Episode V' for those of you keeping track at home. 'Empire' is darker -- and better -- than the original, full of spectacular scenes, sexual tension between Princess Leia and Han Solo and lots of fun dialogue -- something the later sequels apparently forgot. Stars Carrie Fisher and Mark Hamill had a three-picture deal going in; Harrison Ford did not. His character was originally supposed to be killed off, and that's why Solo was frozen in carbonite. His agent must have negotiated a deal to appear in 'Return of the Jedi.' After a scene with the Ewoks, we bet Ford wished he'd stayed frozen.

1. 'Blade Runner' (1982)
A box office dud at the time of its release, this movie has undergone more facelifts than Joan Rivers. Regardless, it's a dark future with film noir elements dripping from every pore. We prefer versions without Harrison Ford's narration, as Ridley Scott initially intended. Joanna Cassidy in a see-through rain slicker, kicking ass, is worth the price of the DVD. Ditto for the skin-job baddie played by Rutger Hauer, a stone-cold killer with a poet's turn of phrase: "I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion ... All those moments will be lost in time -- like tears in rain. Time to die."


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