I was eight in the summer of 1977 when the film first came out. I was thunderstruck. My parents loved going to the movies, and almost always took me and my brother and sister along. I was never really into movies that much, and was basically along for the ride (literally so when we would go to a drive-in; I usually fell asleep in the back seat.)
But "Star Wars" was different. I felt like it was a story told directly to me, that spoke to me and other kids like me. It sparked an interest in the kind of worlds George Lucas was creating right there up on the screen. It was the first film that made me want to know more about the setting of the narrative, and the people and other beings who lived in it. Obviously, the Extended Star Wars Universe that followed didn't disappoint.
Most of all, I loved the dichotomy between what we would think of as a "futuristic" setting, and the notation that the story happened "A long time ago..." I immediately grokked that what was the future for us might be a long time ago in a distant galaxy.
The cynical and world-weary will happily point out that Star Wars is simply the biggest cash cow of all time, a merchandiser's dream. But I'm content to view it as a series of stories about people (and robots, and non-humans) who are remarkably like us, and are fun to watch on screen.