What was the problem with windows phone? Only one, the lack of applications. In Build 2015 the project Astoria was announced, now called Window Bridge, and will enable to build applications for Windows 10 Mobile by reusing Android Code.

With the bridge youÔÇÖll be able to:

• Use a Microsoft interoperability library to integrate Microsoft services into your app with little effort
• Test and debug your app from your preferred IDE
• Publish your app and get paid through the Windows Store

You can subscribe your interest here: https://dev.windows.com/en-us/bridges/android

You can install now (some) unofficially applications on your windows 10 phone.

You can (at your own risk) experiment, installing android applications on your Windows Phone 10 mobile.

http://forum.xda-developers.com/windows-10/windows-10-mobile/how-to-install-android-apps-windows-10-t3174629

There is also a video demonstrating the installation of the Amazon store in a Lumia 920.