1: 'Them' - 1954
2: 'The Thing From Another World' - 1951
Read the original screenplay of The Thing From Another World - August, 1950

3: 'The Day the Earth Stood Still' - 1951
4: 'Earth vs. the Flying Saucers' - 1956
5: 'It Conquered the World' - 1956

6: 'A Trip to the Moon' - 1902 - 16 minutes - Plot: Perhaps the very first science fiction movie ever made, this short film combined elements from novels by Jules Verne and H.G. Wells to tell about a fantastic trip to the moon.

7: 'The Lost World' - 1925 - Plot: Silent film about an expedition into an unexplored jungle teeming with dinosaurs from the Jurassic era. In this version, one of the dinosaurs if brought back to London. Based on the novel by Arthur Conan Doyle. Remake: Lost World - 1960 - 98 min

8: 'Metropolis' - 1926 - Plot: Futuristic German tale of class conflict in a city where the wealthy leaders live in skyscrapers and the workers live underground toiling at huge machines.

9: 'King Kong' - 1933 - Plot: Explorers find a gigantic ape who grows attached to a young maiden; but when the ape is brought to New York City, he goes wild and meets his fate at the top of the Empire State Building.
Sequels:
The Son of Kong - 1933
King Kong Escapes - 1967
King Kong - 1976 Remake
King Kong Lives - 1986

10: 'Flash Gordon: Spaceship to the Unknown' - 1936
Plot: With the planet Mongo headed toward a collision with Earth, Flash, Dale Arden, and Dr. Zarkov fly to the rescue against the evil Emperor Ming.
Sequels:
Flash Gordon's Trip to Mars - 1938 - Also known as "Flash Gordon: Mars Attacks the World" and as "The Deadly Ray from Mars."
Flash Gordon Conquers the Universe - 1940 - Also known as "Purple Death from Outer Space."

11: 'Things to Come' - 1936 - Plot: Prophetic British look at mankind's future, which predicted World War II, followed by disease, revolution, and space travel. Based on the novel by H.G. Wells.

12: 'Buck Rogers: Destination Saturn - 1939 -
Plot: Buck Rogers and Buddy Wade are revived from suspended animation and fight Killer Kane and his space gangsters.

13: 'Dr. Cyclops - 1940 - Plot: A crazed scientist shrinks five visitors to a foot height, with the result that everything around them presents extreme danger. The first science fiction movie to be filmed in color.

yes, there are many more