Here are some sci-fi films you HAVE to have seen (in my humble opinion) if you love sci-fi (update-now in chronological order and links for more info). Disagree? Other choices? Leave me your comments.

Metropolis (1927)
Things to Come (1936)
Forbidden Planet (1956)
The Time Machine (1960)
Star Wars (1977)
Alien (1979)
Empire Strikes Back (1980)
Blade Runner (1982)
Star Trek II: The Wrath of Khan (1982)
The Thing (1982)
Terminator (1984)
Back to the Future (1985)
Enemy Mine (1985)
Aliens (1986)
The Fly (1986)
Robocop (1987)
Predator (1987)
The Fly II (1989)
Back to the Future Part II (1989)
Back to the Future Part III (1990)
Predator 2 (1990)
Terminator II: Judgment Day (1991)
Stargate (1994)
Ghost in the Shell (aka Kôkaku kidôtai) (1995)
12 Monkeys (1995)
Gattaca (1997)
Starship Troopers (1997)
The Matrix (1999)
Donnie Darko (2001)
Primer (2004)
The Island (2005)
Children of Men (2006)
The Fountain (2006)
Star Trek (2009-still in theaters-GO SEE IT!!!)

(future posts in this series will include drama, horror, westerns, and comic book related which is why the above list is missing some films that probably are technically sci-fi but if they were related to superheroes/comics I left out to focus on them specifically).