There is also the question if you can compare a true MMOG with a multiplayer/singleplayer game like NWN or NWN2. I think the audience is a different one here. While people play the newest MMOG because of the fact it is a MMOG the others will play NWN is because they want to play a CRPG with the option of having a multiplayer experience. And additionally a MP experience where you choose to play with a DM or not.
So I think the market for the latter (NWN/NWN2) is higher as for the first one (MMOG), but then I have no numbers to prove this, just my guesstimation
