You won't have resources to translate your mobile game to all possible markets. You should target the markets with the most paying customers.

Here are the languages you should launch your mobile game to cover over 75% of the mobile gaming market:

1. English (USA, UK, Canada, Australia)
2. Japanese (Japan)

For Android games:

+ Korean (South Korea)

For iOS games:

+ Simplified Chinese (China)

These are the next largest markets:

+ German (Germany)
+ French (French)
+ Traditional Chinese (Taiwan)

These are rapidly growing markets but not a must as of 2014:

+ Russian (Russia)
+ Spanish (Latin America)
+ Portugese (Brazil)

Sources

• https://www.youtube.com/watch?v=wm5SoBGdxDU