Top 5 Favorite Sci-Fi Movies
1) Aliens (1986)
2) Robocop (original)
3) Jurassic Park (1st)
4) The Terminator (1st)
5) The Thing (1982)
4 of 5 of these are eighties movies. Considering some other very good eighties Sci-Fi movies I cut from the list (Road Warrior, Blade Runner, Total Recall), I realized that the eighties really must be the greatest decade for sci-fi films.
Two other eighties movies deserve special mention: the beloved Back to the Future (I) and the comedy cult classic Repo Man (1984). Although both of these had Sci-Fi elements, I don't think I can characterize comedies as Sci-Fi (although one could argue that Robocop was half comedy).