iOS App StoreIt’s been a busy, busy year in the mobile world: RIM is all but dead, Android bit a sizable chunk out of the market and Apple unleashed Siri upon the world. As companies churn out one “next best thing” after another, more and more customers are gravitating to the smartphone space. Naturally, app downloads have gone through the roof. Have any guesses on which app store pulled in the most revenue?

According to Distomo’s year-end report, Apple’s iOS App Store was the top revenue-generating OS for developers in 2011. By measuring the top 200 highest-grossing apps for both the iPad and iPhone, Distomo concluded that Apple’s offering bested Google’s Android Market by nearly four times revenue-wise.

That doesn’t mean Apple’s year went swimmingly. Downloads in the App Store were said to have declined for nearly the entire year, with much of that having to do with the oft speculated iPhone 4S release. But once the device finally hit in October, Apple’s App Store reached its highest download peak the month after. In contrast, downloads were at their lowest in September.

All-in-all, the seven major app stores combine to offer more than 1 million apps – every app store was said to have doubled in 2011, with Windows Phone 7 Marketplace showing a 400 percent growth over the previous year.

The interesting bit is how developers earned most of their revenue. “Half of the revenue of the 200 top-grossing apps in the Apple App Store for iPhone is now generated by “freemium” apps. And over at the Android Market, fully 65 percent of the revenue from the top-grossing apps is generated by freemium apps,” said CED Magazine.

For good measure, Distomo included the top downloaded app across all platforms globally. Unsurprisingly, it was Rovio’s Angry Birds.

I know I definitely contributed to the iOS App Store this year. Which store did you download from in 2011?