DFC Intelligence, they take a look at the top money-makers in the MMO space worldwide. To no one's surprise, World of Warcaft has topped the list, followed by several Asian MMOs like MapleStory, Lineage I and II, Shanda and Fantasy Westward Journey. As for the most users, this study doesn't touch on that. With such a wide discrepancy between active subscribers and prepaid game card users, it's a difficult number to tack down.
What makes this list frustrating is the complete lack of details involved. While WoW is reported to have earned $500 million+ in 2008, the next four on the list are reporting $150-$500 million, and the final five are reporting anything in the $50-$150 million range. To the company's credit, this isn't the final analysis. Their detailed February 16th report promises to give more information on each of the top 10 games. We certainly look forward to that.