This comes up each year, and each year it's the exact same thing — Disneyland Park comes in fourth, the Studios come in 23,924th, and then the knowledgeable fans contest, saying the numbers are skewed. First, because it's unlikely that Disneyland or Tokyo Disneyland never beats the Magic Kingdom (and Disney desperately wants the Magic Kingdom to forever be number one), second because the Paris system only counts the first park you enter with your pass. So if you enter the Disneyland Park first, which the vast majority does, then head off to the Studios later in the day, your Walt Disney Studios visit is not registered.
I'm inclined to believe that, because it makes so much sense — everyone buys their tickets at the Disneyland Park gates, of course, and then Main Street beckons... And frankly I don't think I've ever started a day at the Studios. And besides, the number just seems improbably low.
Still, whether the numbers are accurate or not, at least it makes the Disneyland Park seem popular the world over...