The Empire Strikes Back, 1980. I was 3 years old at the time and don't remember much of the experience of seeing the movie itself at that point, outside of a few key scenes: the probe landing on Hoth, Luke vs. Darth Faker on Dagobah, and Han getting carbonized. It must have made an impression on me even then, though, since that Christmas was when I got the earliest Christmas presents that I remember: the yellow jammies with Vader & the droids on them, and the Kenner figures of Artoo, Threepio and Yoda.
I DO remember from that night, though, me, my older brother and Dad, my Uncle Danny and cousin Nate, my Grandpa AND my uncle Steve all crammed into my Grandpa's mustard-yellow Chrysler to go see it at the Westroads theatre in Omaha which I don't think even exists anymore, and stopping by the nearest Winchell's afterwards.