The co-founder of Epic Games, Mark Rein has mentioned that there's still issues in Android that is causing them a lot of headache which is probably why we haven't seen any Unreal Technology games floating around in the Android Market (or even elsewhere for that matter). One of the major reasons cited is due to the limitation of the Android Market in terms of file sizes for applications or games. Some months back, Google had already increased the file size limit of applications in the Android Market to 25MB, this is still not good enough according to Mark Rein.
If we take a look at the App Store of Android's main competitor, namely the Apple App Store, you can see that there are many games out there that are very large in size for instance Infinity Blade is a whopping 800MB in size. While most game developers such as Gameloft have managed to get their games out by allowing their applications to download the game contents separately from their own servers, this is still not the best way to deliver a game to the general consumer as we all know that Gameloft's servers had their own fair share of issues. Check out the source for the complete interview details with Mark Rein.