I think a number of the movies we showed our daughter when she was little were the ones we had loved at a similar age - The Mary Poppins that nineweaving can't stand, "Hard Day's Night," which came out when we were about eight, and had a profound effect not just on us, but on many people our age. And oddities - "Cold Comfort Farm" might not have been the most appropriate choice for a small child, but maybe one can never be too young to know that there was something nasty in the woodshed.
Early movies