Windows.System.UserProfile.GlobalizationPreferences.Languages[0]
This is the correct way to obtain the currently set system language. System language setting is completely different than culture setting from which you all want to get the language.
For example: User may use "en-GB" language along with "en-US" culture at the same time. Using CurrentCulture and other cultures you will get "en-US", hope you get the difference (that may be innoticable with GB-US, but with other languages?)