The key to having a successful platform these days is app support. But because iOS and Android as so well established, app developers are reluctant to spend the time, effort, and money on new platforms such as Windows 10. However, Microsoft's Universal Windows App platform helps to make the process of taking existing iOS apps and porting them to Windows 10 a lot easier.
In the video below, developer - and Microsoft MVP - David Burela took the source code of popular iOS game Canabalt and ported to a Windows 10 Universal Windows Platform app in under 5 minutes.
Now I'm not suggesting that every app is going to be as simple to port to Windows 10, but this does show the lengths that Microsoft has gone to in order to try to make the porting process from iOS, Silverlight and such (no Android support I'm afraid, it seems like that project has been axed) to Windows 10 as pain-free as possible.