The correct answer is NEITHER..
There are bigger openings than HP or P4.
CARS 2
Kung Fu Panda 2
Transformers 3
Green Lantern
Captain America
X-Men First Class
Do you not realize that the
seven previous Harry Potter movies averaged over $900,000,000 gross revenue? The only true competition on that list comes from Transformers 3 when we consider Transformers 2 which grossed $836,297,228. Although given how terrible the first two Transformers movies were (most people gave the first one a pass because of nostalgia and its charms were unique), I honestly don't expect 3 to be as successful
Cars 2 was actually one of Pixar's worst grossing films (didn't break $500 mil), the only reason we're seeing a sequel is because of its wildly successful merchandising. Kung Fu Panda was cute but ultimately a blip on the radar, not even breaching $700 mil (something
every Potter film has done), I really don't see KFP2 doing significantly better.
And as comic book movies Green Lantern, Captain America, and X-Men First Class can only be a contender if they actually turn out to be genuinely super awesome movies (and not just good summer popcorn comic book movies). Really its highly unlikely they'll be more wildly successful than similar past counterparts such as Iron Man 1 which ultimately only drew ~$585,000,000, especially considering they're all being released so close to each other (competition) and aren't sequels (Batman Begins really was no worse a movie than The Dark Knight, but The Dark Knight benefited greatly from the established reputation)
No, it will be Harry Potter in a land slide unless the sheeple eat up another terrible Transformers movie, or if Transformers 3 somehow actually turns out to be a good movie. But even then I'd be surprised if Harry Potter doesn't ultimately pull in the most money.
while Harry Potter fervor has died off a bit ever since the books were finished, the movies have regularly pushed 100+ million dollar openings and of course each nearing almost a
billion in gross revenue, and this is the last in the series so its pretty much guaranteed to draw a large showing
that being said, Pirates certainly doesn't stand a chance to be anywhere near the #1 summer movie, there are just too many summer blockbustsers, and of course its disappointing reviews won't help it keep steam.