The first role-playing system I played in my life was Das Schwarze Auge (The Dark Eye). The next two were Dungeons & Dragons and Midgard. So how did we choose these games? Simply, they were the only role-playing games available in German in the 80's. How many teenagers do you know who are fluent in another language? It happens, if the parents speak different languages, but to most teenagers marketing a pen & paper role-playing game that is not in their native language would be a tough sale. Adults are more likely to speak a foreign language, but pen & paper games are so heavily language-dependent, that playing them in a foreign language is tough. Believe me, because I do.

My current campaign is 4th edition Dungeons & Dragons, and we are playing in French, which is bloody hard for me. But then half of the players don't speak English, so we don't have much choice. And we are also limited in the choice of what systems to play: Not every role-playing system you know in English has a French translation. In fact I wrote a mail to WotC to ask them whether D&D Next would be translated into French, and received a reply that there were currently no plans to do so. 4th edition was still released simultaneously in English and French, but the next edition of Dungeons & Dragons will be for English-speakers only. They stopped translating D&D into German 6 years ago. Pathfinder on the other hand is currently available in both French and German, which helped them beat D&D in sales numbers.

You can play a MMORPG with a lot less mastery of a foreign language if it isn't available in your native tongue. But still there are quest texts to read and NPCs to talk to, so a game simply sells better if it offers multiple languages. Both TESO and Wildstar offer English, French, and German on release, a language selection that is shared by many other MMORPGs like SWTOR or The Secret World. World of Warcraft is in addition to that available in Italian, Portuguese, Russian, Spanish, and Chinese. Especially Chinese makes a huge difference to the potential size of your audience and thus player numbers, not just for WoW, but also for EVE Online for example.

The smaller the game (whether pen & paper or MMORPG), the less likely it is to come in multiple languages. That creates a vicious circle, where the small game can afford only English, but then is limited in growth because it comes only in English. So remember, especially for pen & paper system, if I don't play your favorite system with my group, it might be because of the language barrier.