A milestone hit for the Windows Phone 7 marketplace today, as it was discovered that they just hit app number 20,000 available for download. And what’s even better, at least for those out there who think that Windows Phone 7 will be able to play in the sandbox largely dominated by Apple and Android, is that it took Microsoft almost the exact same amount of time to reach said milestone as it took Apple.

The head to head comparison reveals some interesting parallels. While it took Microsoft fully 219 days to get to the 20,000 app mark, it took Apple just four days less, at 215 days, to reach the same marker. By way of comparison, Android Marketplace took almost twice that long with 419 days to reach 20,000 apps.

And looking at the current state of the Windows Phone 7 Marketplace is equally interesting; fully half of Windows Phone 7 apps are available for free, while most of the remaining apps sell at $.99. The most popular category? Not surprisingly, it’s games.

So now we have a better look at just what’s going on in the Windows Phone 7 camp, and that yields a lot of possibilities for us to look at. The biggest question on a lot of people’s minds is, undoubtedly, can Microsoft compete with Apple and Android in this particular market? We’ve been wondering that since Microsoft first announced it was getting in in the first place, and though we’re still not ruling anything out, it looks like Microsoft may be able to play after all. Obviously, it’s going to have to keep these gains up, but if they can boast the same number of apps as Apple can, and have any kind of differentiation to separate themselves, they’re almost certainly going to be able to knock Android out of the number two slot it’s currently in, and maybe even pose a challenge to Apple itself.