1978.
Believe it or not, my earliest memories of Star Wars are listening to the Return of the Jedi Read-Along Book and Tape. :)
I can't recall when I first watched the movies. I do, however, remember that my parents must have had a pirate copy of "Star Wars" (which I think might have been widescreen) because I can distinctly recall the final shot of the throne room and the thought that the black bars were annoying and stupid (hey, I was a kid and it wasn't explained why they were there). So, obviously I didn't watch it.
But I do remember when my parents gave me the "Faces" VHS box set. I think it was for my birthday.