Found this on The Anarchangel:

"John Scalzi, one of the first bloggers and a starting-to-be-successful Sci-Fi author in his own right; has recently published a book in the Rough Guide series: The Rough Guide to Science Fiction..."

"Well, one of his readers, another blogger has started a fun little meme. In the book, Scalzi lists what he calls "The Canon", much as literati talk of the canon of western fiction etc... this list is about the greatest, most influential, most interesting, most appreciated or obesessed over films in SF history.The meme in question is simple. Just take the list, bold the ones youve seen and like, leave alone the ones you don't care about and strike out the ones you've seen and really dont like."

There are several films I'd list that aren't here and some that caused me to scratch my head, but here's my list

The Adventures of Buckaroo Banzai Across the 8th Dimension!
Akira
Alien
Aliens
Alphaville
Back to the Future
Blade Runner
Brazil
Bride of Frankenstein
Brother From Another Planet
A Clockwork Orange
Close Encounters of the Third Kind
Contact
The Damned
Destination Moon
The Day The Earth Stood Still
Delicatessen
Escape From New York
ET: The Extraterrestrial
Flash Gordon: Space Soldiers (serial)
The Fly (1985 version)
Forbidden Planet
Ghost in the Shell
Gojira/Godzilla
The Incredibles
Invasion of the Body Snatchers (1956 version)
Jurassic Park
Mad Max 2/The Road Warrior
The Matrix
Metropolis
On the Beach
Planet of the Apes (1968 version)
Robocop
Sleeper
Solaris (1972 version)
Star Trek II: The Wrath of Khan
Star Wars Episode IV: A New Hope
Star Wars Episode V: The Empire Strikes Back
The Stepford Wives
Superman
Terminator 2: Judgement Day
The Thing From Another World
Things to Come
Tron
12 Monkeys
28 Days Later
20,000 Leagues Under the Sea
2001: A Space Odyssey
La Voyage Dans la Lune
War of the Worlds (1953 version)