I actually find sci-fi films of the last 40 years have dated far more than older films like "Metropolis". I think that this is because many of these films depend too much on their design and wardrobe to create a "look" that ties them to the time they were made, and sci-fi films especially can't get away with it. E.g., "Soylent Green", "Tron", "Equilibrium", "Terminator".