The Empire Strikes Back
This was the second movie I saw as a child (the first was Star Trek: The Motion Picture; I was 6. I remember very little from my initial thoughts other than:
1. Being scared to death of Darth Vader. His costume. His persona. His hissing breath. He was magnificently scary to an impressionable kid. I remember starting very dramatically when, as Luke is sneaking back into the building after Vader's use of the force knocked him out... He's sneaking back in, looking this way and that, in utter silence. Only the sudden hiss of Vader's breathing alerts him in time to dodge what appeared to be a killing blow right before Vader proves that Luke never had a chance in their first confrontation.
2. "The Imperial March!" That's what I fell in love with symphonic music (alas, I don't play)! There are few musical experiences beyond those while watching a Star Wars film. Although Williams struck gold with the Theme from Jaws, The March from Superman, and the Star Wars Fanfare, I am convinced that his crowning achievement was The Imperial March. I mean, not only does it perfectly identify with Darth Vader (and, until The Emperor's Theme, the Dark Side of the Force), it's music that truly captures goose-stepping, heartless, tyranny. BRILLIANT!
As far as the "original" edition and the Special Edition... I think that most of the changes in the Special Edition of this film were unnecessary. Aside from Cloud City, I can't think of a single change that was necessary. The icebeast wasn't necessary; adding that asinine scream when Luke falls down the shaft wasn't necessary (if anything should have been here, it should have been Vader stopping Luke's fall before letting him go which was in the original script); that whole cutting of the escape from Cloud City with Vader asking for his shuttle and repeated shots of the shuttle getting to the Executor wasn't necessary. So, I went with the original cut.