I'm just wondering which language(s) have the biggest fanclub in your opinion.
My impression is that Finnish is definetely on the list, because not only almost everyone loves it, but those who do, love it a lot.
Icelandic and Japanese also come to mind. Icelandic because it's relatively widely studied for such a small language, and Japanese for obvious reasons.
In contrast, English, Spanish, French and most of the big guys seem to be studied by need rather than passion most of the time. Which means they don't have too much fans.
English doesn't have that many fans. Most are forced to learn it at one point or another. I would say Japanese (thanks to Anime) and French (god knows why...) have the biggest.