Some constructors of WinRT types accept an IEnumerable<string> of languages to try in resolving a choice of language. For example, there is a Windows.Globalization.NumberFormatting.CurrencyFormatter constructor that takes a list of languages to try in determining the choice of language of the currency formatter.
The only method I know of to access the user’s language is to default-construct a Windows.Globalization.Language object and access the Id property. If the user has set a list of preferred languages, how is it possible to obtain the full list in the priority order that they specified?
I think this property is what you need:
GlobalizationPreferences.Languages. See the MSDN page on the GlobalizationPreferences class for more info.