Apple’s App Store today announced 2 billion downloads. Apple marked the milestone in a press release along with a fresh batch of data for the App Store.

According to the release, the App Store now offers more than 85,000 downloadable apps, which it says are available to 50 million iPhone and iPod touch customers worldwide. Additionally, Apple says there are now more than 125,000 developers in the iPhone Developer Program.

The App Store has set a high standard for the pack of emerging OEM and carrier-branded mobile application stores. According to most app analytics sources, the Android Market comes in at a distant second, with an app catalog of about 10,000. However, developer interest in Google’s open-source platform has increased significantly over the past few months, providing the first indications of real competition for the App Store.

Analytics from Flurry, a mobile app analytics company, show that Android saw some 200 new applications begin development in July. That’s up from less than 50 in March. And while the iPhone might have seen 800 new application starts in July, Android supporters can be encouraged by growth on several fronts, including new summer handsets and promises of more to come in 2010.

Additionally, Pinch Media, another analytics company, recently released data that found incredibly low retention rates for iPhone applications. For instance, only 20 percent of users return to use a free app 24 hours after download. Thirty days after download, only about 5 percent of those who downloaded the app are still using it.

Taking into account the number of “fluff” or free apps at the App Store, as well as Pinch’s retention data, critics say that Apple’s data is marginally misleading. Nevertheless, the App Store remains the envy of many OEMs and carriers.

Meanwhile, Apple has had to contend with criticism over the App Store’s approval process, as well as an FCC inquiry into its handling of the Google Voice app. In response to the FCC’s inquiry, Apple stated that it had not rejected the app, but rather was still reviewing Google Voice. However, Google last week refuted that claim, saying Apple flatly rejected the app. The FCC is still looking into the matter.