Ever heard of Planet of the Apes or Wizard of Oz?
People act like Star Wars created cinema merchandise when it did not. It only amplified it. Planet of the Apes especially had a lot of merch like toys, games, shows, etc following the films in the 60s.
Lucas got the merchandising rights to SW as part of his contract because the studio thought they were right next to worthless.
That should tell you exactly how 'amplified' SW made merchandising.
I bet a lot of kids woke up on Christmas day, opened their presents to a Planet of the Apes playset and thought 'wtf is this, where are the spider-man web-shooters I asked for?'
Whereas with Sw toys, the parents would be fighting over the last At-At in the shop because it was either that or a trip down to the bargain basement shop for a Planet of the Apes playset, and an abiding memory of a massive 'wtf' embedded in their child's memory.
I saw ESB in 1980, but did not really get into Sw at that point, I got a few of the non-humanoid action figures to use as superheroes when playing, such as Darth, C-3po and a couple of Hoth Stormtroopers. Part of the reason I didn't get into SW initially was because it was so popular, and I did not want to follow the crowd, I had my superhero comics and toys thank you very much. I thought it had to be a lot of overated crap, like most movies when the 1st movie was released.
Also, we did not have a video recorder, so i could not rent the movies, i enjoyed empire well enough, but was only about 6 when i saw it, and only saw it the once. But, when they showed the first Star Wars film on tv in 82, I got heavily into it, and started getting all the toys.
There was nothing like it, it was everywhere.
In comparison to Potter, it's different medium, but I don't imagine there are anywhere near as many kids at home running round the house with their dad's specs on, while riding the house mop, as there were kids using the house mop as a lightsabre, or y'know, playing with SW toys.
With Potter, I imagine for the most part, the kids read the books, and that is about it, they watch the movie dvds and maybe they buy a wand that makes some crazy magic sounds and get some enjoyment out of it for a day. But with SW if you were into it as a kid, it became a way of life. You had to get all the figures, all the ships, all the comics, it was like being hooked on death sticks.