Being born in '77, ROTJ is the only installment of the OT that I remember seeing in theatres. Prior to seeing it, I remember buying a package of ROTJ cookies that were shaped like the characters, and being excited about seeing who the "pig guys" were going to be. My parents had also bought me a Bib Fortuna figure, and I thought he looked really neat (I liked that his cape was made of cloth, unlike the plastic capes that my Vader and Obi-Wan figures had).
When I saw the movie itself, I thought it was fantastic. I remember thinking how cool it was to finally see Jabba after hearing about him in the previous two films. I also liked the Sarlaac pit and speeder bike sequences (for years afterward, any time I played with my SW figures outside, I'd dig a hole in the sand and throw my guys into the Sarlaac). And, of course, I thought the Royal Guards looked pretty awesome.
The coolest thing for me as a kid, though, was the "drama" of the whole thing. The conversation between Luke and Leia at the Ewok village, Han finally dropping his guard and saying "I'm sorry" to Leia, Ben telling Luke the truth about Vader, Vader and Luke's conversation before being taken to the Emperor-- it all felt very epic to me, like the story and the characters were really culminating in something big and emotionally satisfying, and that is what, to this day, keeps me digging this movie.