Lifelong Trekkie here, so of course honor decrees that I have to say all of the ST movies, and of course the original series.

One of my favorite sci-fi's from my childhood days (I'll be giving away my old age here) was a 1959 classic titled Angry Red Planet.

Not a movie (yet) but I'll shamelessly give a mention to the Mass Effect trilogy, my favorite space series of vgames of all time.