This one is going to be bizarre, but the first movie I remember seeing (actually it was my second movie I went to see ever) was Disney's "Song of the South." There's a lot of controversy about this film nowadays (Disney pretty much refuses to release it on DVD or VHS or Betamax or 16mm in the US ever again), but I do recall going to see it in a small town theater when I was a kid. I can't remember how old I was or what year it was, but that's my first memory of a movie theater.
My mother and aunt actually took me to see "Star Wars" in 1977 but I don't remember it (I was far too young). My mother told me later that I did not make a peep during the entire film and that when Darth Vader took his first step onto the Tantive IV, I began rocking in my chair and smiling and cooing, so I guess things were predestined from that point.

I also remember seeing the Robin Williams "Popeye" movie at a drive-in in that same town when I was a kid, but again, I don't recall the age.
I also consider myself lucky to have seen Weird Al's "UHF" and The Transformers Movie in theaters during their opening weekends (I still have the DVD of "UHF" in my collection and it still holds up as a hilarious film).
"Badgers? WE DON'T NEED NO STINKING BADGERS!"