Android App - My Game Collection
This website came is an extension of My Game Collection for Android (also compatible with Bluestacks on Windows & mac), but is also very usable without the app.
More information on My Game Collection can be found on the Google Play Store or its website.
In My Game Collection (Android app) you can export your collection to the website by clicking 'Share to Cloud' in the main menu under menu group 'DATA'.
The image below give you an idea of what My Game Collection is: