Number one for me is Seksmisja - Polish movie created under communist regime. It's a sci-fi comedy with I watched at least 50 times and it's still good 🙂
Second is Alien and sequels. It became part of mass culture. The same on second place is Back to Future and sequels. Star Wars 3-6 is there with Mad Max.
Third place would be Fifth Element, Matrix, Contact, Stargate and Mr. Nobody,