Silicon Alley Insider has posted an interesting chart that shows the total number of apps available across various mobile platforms. As you can see from the chart, Apple's iPhone leads the pack by a longshot with 170,000 apps according to AppShopper.com. AppShopper typically lists more apps than Apple publicly states it has because AppShopper updates its numbers on a daily basis. As of today's count, AppShopper says Apple has approved 198,924 apps with 171,722 available to download. The discrepancy between the numbers accounts for apps that either the developers or Apple have removed from the App Store. Apple officially states that it currently has 150,000 apps.
A distant second after Apple's App Store is Google's Android Marketplace with 30,000 apps. RIM's Blackberry trails with only 5,000 apps, while Palm has a paltry 2,000. Windows Phone 7 Series Applications were announce a few days ago with a limited number of developers signed on. Of course, these numbers don't take app quality into account at all (100,000 fart apps is still just a bunch of junk), but clearly in terms of available downloads, Apple has a huge lead.