It's no secret Apple has been tremendously successful with its iPhone and iPod touch App Store -- after all they like to remind us every once in a while. But learning their actual grasp of the market compared to rivals can still be surprising considering they've accomplished this with three generations of just a single device in roughly eighteen months. As it turns out, Apple's store was responsible for almost all mobile app downloads in 2009.

According to a recent study from market research firm Gartner, smartphone users downloaded 2.516 billion apps last year, including both free and paid ones, totaling around $4.2 billion in revenue for those selling them. Apple alone accounted for 2.5 billion downloads, giving it a market share in excess of 99%, and since it takes a 30% commission from all sales, also a fair bit that revenue to boost its bottom line.

Gartner estimates the explosive growth in the mobile app market will continue throughout 2010 with 4.5 billion downloads, good for about $6.2 billion in revenue, rising to 21.6 billion downloads and $29.5 billion revenue by 2013. A majority of those apps will be free. Still, the good news for Apple competitors is that with the emergence of new players the iPhone maker's share of the market could fall to around 66% this year.

Keep in mind that Gartner's figures appear to focus on manufacturer-based stores only, and not carrier-based or third-party stores such as Cydia, so the actual percentages may be a fair bit off. It still goes to show Apple's incredible dominance in this space and the huge revenue opportunities for developers going forward.