"Order of the Phoenix" did more business in five days than each of the first three "Harry Potter" movies did in their first full week, and it nearly matched the $146 million first week total of the fourth film, "Harry Potter and the Goblet of Fire," Fellman said. from LA Times.
I know that last fall I was interested in seeing what movies would be out when this summer. I looked and it seemed like every two weeks there was/is something coming out, and that's just the big name blockbusters. When you throw in some independent films, you have the potential for being at the movies every week or two over the summer.
Now, for the average family of one/two parents and two kids, this summer saw a lot more entertainment pulling at their wallets than normal.
From May on: Spiderman 3, Shrek 3, POTC AWE, Fantastic Four, Evan Almighty, Ratatouille, Transformers, HP Phoenix, Simpsons.
Those are just the biggies. The movies that the name or franchise alone will get people into, not the other sleeper family movies or the horror movies that attract the teens. Add in the Potter book at $20/book, and two or three books a family, and you are making for an expensive summer for a family. If there is one or two people that are buying a movie ticket, that is different than a family of four or five going to see one movie two or three times.
http://www.usatoday.com/news/nation/2001/12/02/movie.htm
Most of the other Potter movies have been released around Thanksgiving, having that holiday weekend, as well as the school break for Christmas to give it a boost of repeat business.
While both POTC and Potter are sequels, and appeal to the same audience, you can't expect the same conditions to apply to both movies. That would be like saying that since Madagascar and The Wild are similar movies, they should have grossed similar, peaked the same time, dropped off the same way, etc.
As far as the Narnia debate goes, you are overlooking something that I can guarantee that the executives at Disney took notice of. They received praise for that movie from Christian audiences, which can be rare for Disney. I think if they think they will be able to pander to that audience in even the smallest way, they will. I didn't read the whole series, but do they need the original kids to finish the series. They ran into a problem with A Series of Unfortunate Events. They adapted it well, but it should have all been filmed as quickly and closely as possible. Darn kids going and growing up....