Analyst firm research2guidance has a published a report according to which, while the number of apps submitted to Android Market has passed the 500,000 mark, compared with 600,000 for Apple’s App Store, more than 37 percent of these have subsequently been removed – compared with just 24 percent removed from the App Store.
The report is as follows
The actual total number of applications published on the Android Market leapt to over 500,000 in September 2011. In the meantime, the Apple App Store stands at just over 600,000 successful submissions: just 20% more. But over 37% of the applications published were later removed from the Android Market for various reasons, whereas the Apple App Store has removed just 24% of published apps in comparison, as of the end of September.
Although Apple regularly cleans up its store from inappropriate or outdated content, its active application share still exceeds that of Android. It is likely that the more rigid application submission requirements prevent developers from publishing multiple trial or low quality applications whereas publishers in the Android Market place a lot of market testing, trials, demo and malware content. Over 78% of the apps removed from the Android Market were free, which could mean that publishers put more effort into the applications they place with the pay-per-download business model, thus ensuring that it is kept longer in store.
Android developers are significantly more productive than Apple’s. The average publisher on Android has placed more than 6 applications in the Market since launch, compared to just over 4 apps on average that have been published by iOS developers.
Over the past few months, the Android Market has been maintaining an exponential growth, but is still lagging behind the app store market leader, Apple. In Q3 of 2011, the number of active mobile applications in the Android Market stood at 319,161 compared to 459,589 in Apple App store.

Regarding the Windows Marketplace, the report stated
The share of deactivated apps in the WP7 Marketplace today stands at just 13%. However WP7 Marketplace is a comparably young store and many publishers are still exploring its potential. Fifteen months after its launch (comparable to the WP7 store now), the Android Market similarly had 86% of its apps active and a significant application store clean-up didn’t get started until the end of 2010.
Though there is no mention of the Nokia Store (previously known as the OVI STORE), we can assure you that there are a lot of useless/rogue/low quality apps in it, and the removal percentage of apps from the Nokia Store is very less, when compared to Windows Marketplace.