What are your top 5 sci-fi movies of all time?

I like Alien movies but in the way I like ghost movies. I don't believe in ghosts but I suspend the disbelief.

 I really don't see human beings traveling to other star systems in the next 500 years.  When we do, it will be for just entertainment/recreation.  All serious businesses like exploration can be better done with robots as the advancement in AI will be much quicker than that in flight technology.

  And if we go to another habitable planets, we will make sure there is no alien life form there.  Gosh be serious, if I see a ruin of Alien ship I will run like hell in the opposite direction. Even vegetation(or something similar to it) will worry me to death. 

BLADE RUNNER

THE DAY THE EARTH STOOD STILL (1951)

ALIEN

PROMETHEUS

METROPOLIS (1927)

Alien

Aliens

The Thing

The Day The Earth Stood Still

Moon

Alien (and its sequals)

2001 A Space Odyssey

Close Encounter of the Third Kind

A.I The Artificial Intelligence 

Arrival

Honorable mention: Eternal Sunshine of Spotless Mind

I don't think I could narrow it down to five--Much less in order.

Very Tough to pick 5 and I cannot order them as if one is better than the other, so my five favs:

2001 (1968)

Silent Running (1972)

Alien (1979)

Blade Runner (1982)

Star Wars (1977)

Can't just do five so also:

Outland (1981 - Sean Connery with a shotgun in High Noon in Space!)

5. Star Wars Episode IV: A New Hope

4. Rogue One: A Star Wars Story

3. Star Wars Episode VI: Return of the Jedi

2. Star Wars Episode V: The Empire Strikes Back

1. Jurassic Park

Alien (1979)

Prometheus (2012)

Star Wars (1977/1980/1983)

2001 (1968)

Heavy Metal (1982)

1) Alien

2) Aliens

3) Blade Runner

4) The Thing

5) Predator

Event Horizon, Sunshine, Cube, the Alien franchise, and Terminator: Salvation. Sorry about that last one, haters...!

1 Contact 

2 Prometheus 

3 Alien 

4 Arrival

5 District 9