I wouldn't mind having a really impressive cinematic like
This or
This as television advertisements for GW2. It seems like they would be able to make a pretty big return on it considering how easy it is to own a GW game.
In my case I heard about GW from a friend. Before that I didn't even know about its existence. It was all pure chance I happened to be in the right place at the right time to meet this person, so there is no way I would have ever known about GW had it not been for this chance encounter. Before then I had never really looked into fantasy RPGs. However, if I had seen one of those trailers on TV I would have been impressed enough to at least check the game out, and from there probably buy the game.
It seems like the main problem GW has is that there's such a limited pool of people that know about it. And most of those are die hard fans of other RPGs that scoff at the very notion of GW. If they broadened their advertising campaign beyond word of mouth I think they could easily dominate the market.