Hardcore sci-fi fans like to draw a distinction between the fantasy and science fiction genres. They would probably decompose your list like so -- Fantasy: "Star Wars", "Buck Rogers", "Back to the Future"; Science Fiction: "ET", "Close Encounters", "Battlestar Galactica". I've never seen/read "Space: 1999" so I wouldn't know where it belongs.
Star Wars, Close Encounters of the Third Kind, Battlestar Galactica, Space 1999, Buck Rogers in 25th Century, ET, Back to the Future...
And I'm going to get massively downvoted if I don't mention Dr. Who....