I see many google ad's here for other mmorpg's so how about taking over those positions? Advertise on forums of other games.
Many other game-review sites arround to avertise on. Several already mentioned. Always a source of finding new games, atleast for me.
You could also advertise on other "media" sites like sites of popular tv channels, webradio sites, etc. Maybe even just on popular chat sites. Those usually has users that look at the screen for a longer period of time, with longer banner display times.
As for the targeted audience, I assume you guys can get accurate info about what the "best" (aka most paying) audience is for
EU.