Not where. We can all list off a dozen places where, but that's not the important part. The important part is how.
Given realistic circumstances how would you convey to someone casually glancing at your advertisement the depth of character building that CO possesses?
How would your advertisement pull their eyes away from the no doubt nearby bigger-name advertisement that is likely to be making the same claims?
How do you sell the graphics to a generation mesmerized by next gen graphics?
Realistic circumstances means it's likely to be a standard-sized banner on a website. TV commercials are unrealistic, as is any sort of official professional blog (we already have sites talking about our "content news" and it's unlikely that a big-name siteis going to do a piece on a five year old game... unless it's to trash it with four year old information of course).
The suggestion to advertise the game comes up frequently, but whenever I picture these advertisements in my head, I also picture the average potential customer glancing at it briefly and then never thinking about it again.
Feel free to break any of the rules I've set forth because I know you will anyway