With Marvel, you've pretty much got each solo movie with their own filmmakers who the producers can let work their magic.
I think it's hard to really compare them. But if the story turned shitty by book 5 or if audience interest dwindled to unprofitable by mid way through the series, it would have been a much larger failure in terms of expenses. Harry Potter got dropped right at the peak of Pottermania, it basically could not fail. It's like if the first rings movie failed, the whole thing would keel over, but it's only 3 movies. But they could've culled from the sil or hobbit for more lore. The same is pretty much true of the rings trilogy. While I agree about the stories neatly packaged into yearly developement/episodes. There were more variables at play with Harry Potter. Audience reception to kid actor turned into adult actor. One of the books not turning shit and derailing the story. Dealing with the death of one of the main actors part way into the series. Racing the clock on a cast that is growing physically.
I'd say Lord of the Rings beats it, when you consider the depth of material they had to draw on and only one Peter Jackson to do it with.
