Movie Spoilers

Warning! If you don't want to know the endings or surprise plot twists to hundreds of movies, go no further! Turn back now!

2001: A Space Odyssey (1968)

Dave is sucked through a stargate, and ends up seeing himself very old, and dying. Then he disappears. Then Old Dave sees another monolith, and then there’s a space-embryo that looks like Dave. The End.

Followed by:
2010: The Year We Make Contact (1984)