One thing that Windows Phone and iOS are missing since tge begging is a built-in file manager. File managers are very popular on Android devices as they give you a lot of options like deleting system apps, fixing permissions of different apps as well as editing system files.
So File Managers almost give you full control over your phone. Android has them since the beginning whereas Windows Phone and iOS are lacking this feature. On iOS you have to Jailbreak your phone in order to get File Manager privileges.
However, things are going to change with the next version of Windows Phone, Windows Phone 8.1. The developers have confirmed File Manager support on the next WP update.
All this started with a request at the Requests page on the official website of Microsoft. This requested quickly got over 77.770 votes and so, it got approved. You can see the original page with the request here.