I enjoy making these lists, but for me, I really have to narrow it down because there are so many sci-fi flicks I like.
Top 20 Sci-Fi (in no order - plus I'll mention ones not listed by other members)
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Split Second (1992) - A mysterious and monsterous killer stalks London in the near future. My favorite Ruger Hauer movie next to Blade Runner.
Galaxy of Terror (1981) - Wild and weird space horror movie. Stars: Robert Englund, Sid Haig and Ray Walston
Green Slime (1969) - Rapidly multiplying monsters attacking a space station. Featuring one of my favorite B-movie actors, Richard Jaeckel.
Starchaser: The Legend of Orin (1982) - Humans vs androids in this galactic animated adventure.
Prometheus (2012) - An incredible prequel to the ALIEN series.
The Avengers (2012 - Marvel superheros in a live-action movie, I loved it.
Iron Man 2 (2010) - Tremendous sequel which also included other Marvel characters the Black Widow and War Machine. Amazing cast with Robert Downey Jr., Gwyneth Paltrow, Sam Rockwell, Mickey Rourke, Samuel L. Jackson and Scarlet Johansson.
Captain America (2011) - Super cool to see yet another great Marvel superhero in live-action. Excellent film!
Spider-Man (2002) - Director Sam Raimi did a fantastic job bringing New York's web-slinger to life. I like this movie far more than The Amazing Spider-Man.
The Incredible Hulk (2008) - Extremely improved movie compared to the slow drama of the 2003 film. Great action and exciting to see the Abomination battle the HULK.
Godzilla: Final Wars (2004) - My favorite giant monster helps Earth battle against an alien invasion. Godzilla fights many of his old foes.
Mystery Men (1999) - Very funny comedy about superheros in the near future.
Message From Space (1978) - Far-out weird yet cool space adventure, inspired by Star Wars. Stars: Sonny Chiba and Vic Morrow.
Leprechaun 4: In Space (1997) - Actor Warwick Davis returns to help create one the strangest movies ever made.
Event Horizon (1997) - Actors Laurence Fishburne and Sam Neill appear in this gory space film.
Day of the Triffids (1962) - Excellent film about a meteor shower blinding people along with giving rise to dangerous plant monsters, very clever idea.
Gamera: Super Monster (1980) - You have to be fan of the giant flying monster turtle known as Gamera to look at this mutant's strangest movie. This film borrows ideas from Superman and Star Wars, then throws in clips from previous Gamera films into a oddball mix of goofy fun.
As an added bonus on the DVD, the lovely horror movie host ELVIRA, comments about the film.
Indiana Jones and the Kingdom of the Crystal Skull (2008) - I dressed up as Indiana Jones when this movie came out and I was thrilled to see another action-packed Indy flick. Ancient aliens, I loved it.
Horror Express (1972) - Actors Christopher Lee, Peter Cushing and Telly Savalas star in this very cool movie which was inspired by the story "Who Goes There?", written by John W. Campbell (which was also made into The Thing From Another World (1951) and John Carpenter's: The Thing (1982).
Zeram (1991 - a.k.a. Zeiramu) - A female bounty hunter from space travels to Earth to capture a bio-engineered fighting machine, but things get messed up when she runs into a couple of human repair men. Violent, gory and sometimes funny, but a great film.