Yes, lurkers, like me, who drop in a post only every so often, make up a large chunk. But, for statistics: PBW has 750 registered and perhaps 200 active Users. I also play Black and White, a bazillion-copy seller--and their forums have probably about the same number of actives, maybe 200. I think _that_ says a chunk. Perhaps more about the community, but any game that can create such a large community following is bound to be doing well.
LL
http://seiv.pbw.cc/