Alien/Aliens/(3 &4 in the series are garbage: In our family "verse", Riply made it home with Hicks, Newt and Bishop. Hicks & Riply got married, adopted Newt and they all lived "happily ever after)/Prometheus
2001 a Space Odessy
Star Wars 4 "A New Hope"
The Fifth Element... "Where did he learn to 'negotiate' like that?" ... I wonder.
Honorable mention,no specific order (Yes I know... some are guilty pleasures):
[B]Star Trek II The Wrath of Kahn
Star Trek[/B] (2009)
Matrix Reloaded, Matrix Revolution... Because they wrapped up all the story lines
War of the Worlds (2005) Provides an honest portrayal into how ordinary people would react.
Sky Captain and the World of Tomorrow: This movie was ground-breaking and multitudes of Sci-Fy and other movies that have created complete universes and sets out of nothing but "green screen" owe this movie, its director, the exceptional cast of top quality actors (who worked on the film for peanuts because they realized the vision), along with all of the countless CG people who worked on it a tremendous debt of gratitude.
Avatar (Dances with Wolves in Space BUT the scope of the visuals and the technology to bring it all to pass... nothing short of ground breaking)
Star Wars 3 Revenge of the Sith
Star Wars 5 The Empire Strikes Back