Answer
Blade runner is an amazing one, but it's more dystopian futuristic with some aliens
than like signs or close encounters.
war of the worlds (with tom cruise) is a
nice
one,
exciting and some wonderful effects. the original story from the 30s by h.g. wells scared the pants off a lot of people.
alien (directed by ridley scott, who also directed blade runner) is
scary and also amazing.