What
gottacook said about books. I think the first "grown-up" book I ever read was The War of the Worlds by H.G. Wells, and I was an omnivorous reader of sf, fantasy, and horror from early on. My local library was brimming over with books by Wells, Asimov, Bradbury, Matheson, Sturgeon, Andre Norton, Edgar Rice Burroughs, Olaf Stapledon, etc.
Plus, we should recall that classic sf movies like Forbidden Planet, The Day the Earth Stood Still, War of the Worlds, The Time Machine, This Island Earth, The Incredible Shrinking Man, and so on were still airing regularly on TV back during the sixties and early seventies, while the Planet of the Apes movies were still going strong in the theaters, so even if (God forbid) STAR TREK hadn't happened there would have still been no shortage of memorable sci-fi to warp our tender minds.