re: I just finished The Empire Strikes Back...there's nothing in the prequels...

Star Wars (episode 4 for the younger guys) set the table like no other movie. People see it now, and compare it to films like (for example) GOTG, and say, "what's the deal, these other movies were just as fun". Unless you were there at the time, you really just can't grasp how much everything since, is just a development of it.
In a way, it's like John Browning's old 1911 Colt pistol. People now look at pistols and say "well, this does ___ better than the 1911, it's a better gun", and lose sight of the fact that basically every single pistol we see, is clearly just a further development or variation of that original concept.

Before Star Wars, you had Disney. Animation. Because, simply, you could not present certain things in a believable manner with live action, it HAD to be a cartoon. Star Wars gave us epic space fantasy, superheroes with real super powers, serious fantasy movies at the A level instead of B movies.

Empire is the greater dramatic achievement, but not the ground breaker the original was within the medium.