Please don't take this the wrong way Paul but you're wrong.
I kid, I kid.
Of course I am a huge fan of the books.
I think this, more than anything, explains a great deal of the divide some of us feel for this series. The people who
truly love these films do seem to be readers of the books, and you can see this from how each film performed commercially, wherein the Potter fan base supported the movies early and often before they tailed off (though not before making a fortune). That fan base has dwindled through these lame Fantastic Beasts movies, while they have cultivated no "outside" viewers at all. Yet people love the original Potter movies because they also love the books and the story they tell.
But I'll be honest, taken as a whole, I think they are better than the Star Wars or Star Trek franchises. Potters 5 and 6 were a low ebb -- but still better than Attack of the Clones, Star Wars 7-9, Star Trek: Nemesis and Star Trek: Into Darkness. Certainly as a continuous narrative they are more interesting and hold together better.
I just look at them all a little differently. The Potter movies are book adaptations, with a pre-established story line, and I'd argue that's a whole different thing (not to mention a major advantage for putting a coherent string of films together). I'd also say they were adaptations that, reportedly from everything I've ever heard, very rarely took any chances and veered off the path of the books -- they are slavish (likely to a fault at times) to the source material, and were made not long after the books were published. They didn't take liberties with the books and they weren't meant to -- they were intended to deliver a movie mostly for fans who already knew where the story was going, to "respect" what was already there, and obviously they succeeded wildly on that level.
I do know what you mean in assessing a narrative that holds together over the course of a group of movies -- but again, the Potter pictures are adapting source material that already existed, made all consecutively pretty much over a set amount of time (not, in the case of Star Wars, many years removed between installments). I'd say their degree of difficulty was lower, not to mention the Star Trek movies never set out to tell a 9-movie narrative (and Lucas can say whatever he wants, but he clearly figured out Star Wars for the most part as he was going along too. The pre-established blueprint he always claimed to have was pretty loose there lol).
The Trek and Star Wars movies may have had lower points, no doubt, but -- and this is entirely subjective -- the higher points hit much higher than the Potter films...for me. Personally I do like STAR WARS, EMPIRE STRIKES BACK and RETURN OF THE JEDI better than any of the Harry Potter films. I like several of the Star Trek movies more than any of the Harry Potter films also.
I just feel like the Potter movies mean a
lot to their fan base and I wouldn't ever argue otherwise. Yet for "casual viewers" or anyone who didn't read the books, they are less appealing and did not engage so much outside that group -- especially as it progressed after the first couple of movies. They are more successful in my mind being "good book adaptations" than really great works of cinema.
And I do think STAR WARS, the original, as a piece of cinema is on a whole different level than anything in the Harry Potter film series. George Lucas had to go out and create a galaxy basically all on his own for those movies that didn't exist on the printed page. Yes Star Wars was inspired by Flash Gordon yet it's a milestone of cinema for its technical elements, editorial work, FX, sound effects, its scoring, even its script -- as a standalone entity people forget how integral the movie was to the language of contemporary cinema and raised the bar, far above other genre movies Hollywood had ever made before. That's something that was realized on film, created for that movie, and wasn't around before it -- certainly not in "that way." Nothing looked like it, or sounded like it either (even the sound design was something entirely unique).
The Potter movies adapted something Rowling had laid out for them on a silver platter in terms of narrative, language, and everything else. Yet they work because the story works, less so because the movies themselves (at least
many of them IMO) are particularly inspired. If that makes sense.
Again just my two cents!