Pretty rich category of films to draw from - curious your favorite sci fi films of all time. These can be movies about space, but doesn't have to be. Really any movie that deals with science fiction of any kind qualifies. Welcome to list the obvious classics and throw in some little known ones that you think deserve more attention. Whatever you like.
Here are 15 of my favorites. Definitely not the full list and not necessarily in ranked order, but these are ones that immediately come to mind:
2001: A Space OdysseyInceptionThe Matrix (only the original)ArrivalEx MachinaSunshineEternal Sunshine of the Spotless MindWall EJurassic ParkInterstellarThe AbyssThe SphereContactHerSpirited AwayIf you are looking for some help or a good memory jogger, RottenTomatoes has their 110 Best Sci-Fi Movies of All Time list.
Good list. Stole many of mine so as to not repeat I'll throw a few that I think need to be added for consideration:
Back to the FutureAlien and AliensPlanet of the Apes (just the original)The Terminator 1 and 2Close EncountersETChildren of Men
Really looking forward to the upcoming Dune film. Director of Arrival and Blade Runner 2049 is doing it, Hans Zimmer doing the score.. should be good. Maybe great.
Also recently saw Ad Astra. Not an all time great, but visually the best looking space film I have ever seen so thought it worth a shout out here.