I was five years old when I saw Star Wars, and that movie changed my life. I had seen other movies before, and enjoyed them, but Star Wars gave me what felt like a whole new world. The sheer amount of detail, the sense that the "reality" of the movie went past the edges of whatever image you were seeing, the feeling that this was a place that was lived in, that had history. Nothing before had come close to that.
Avatar is, to my mind, the first film to move beyond Star Wars for the depth of the experience. Note, I am not talking about emotional depth, but sensory depth. The extent to which you get that "you are THERE" feeling.