This page contains a chart displaying best-guess subscriber numbers (as of April 2003) for a dozen different massively multiplayer games. It's focused towards graphical MMOGs that are popular in the U.S. (it doesn't include text-based MMOGs or any of the monster Korean games), but is still some interesting data.

Related factoids that I acquired from E-3:

- Star Wars Galaxies, opening next month, has had about 500,000 people visit its website and apply to be beta-testers.

- Of those 500,000 visitors to the SWG site, 10% were female

- EverQuest reports that its own subscriber-base is 16% female

It'll be interesting to see how the SWG numbers convert into subscribers!