Via MMOCrunch.com I found that the MMOGData site is now hosted by Voig.com, so I thought I'd post a link for reference. MMOGdata is working in the tradition of the apparently abandoned MMOGChart.com of Sir Bruce. But I must say Sir Bruce's site was better in that he only counted actual subscriptions. MMOGData on the other hand counts accounts, thus giving Second Life with it's 4 million accounts a 12% market share, although there are only 40k maximum concurrent users and less than that paying subscribers.
What we would need would be a site counting only monthly subscriptions. That would even take down WoW a couple of notches, because more than half of their customers are in China now, paying by the hour. Or even better we could count annual revenues instead of player numbers. Too bad this sort of data isn't available.