To be honest? If we're being ambitious and going with the "Bungie needs to make an absolutely amazing video game to even come close to following up Halo" mentality, I'd like to see 50 - 100 mi^2 of explorable land per planet. In reference to the picture above, assuming there's 7 planets explorable in this game (which I think is highly likely), that would put Destiny at a world (in total) with an area almost 9 times that of Vanilla WoW (80 mi^2), 33% bigger than Just Cause 2 (400 mi^2), and being just around 100 mi^2 larger than Test Drive: Unlimited (618 mi^2). In my opinion, this could be one of many "big things" that could push Destiny from "oh look... a Halo MMO" to something that could be really popular. e: That doesn't include all the Space areas you can travel through in your customizable ships, so keep that in mind. Also it doesn't factor in any aerial travel one could have on any given planet. However, I don't feel like measuring game worlds in volume (nor does anyone else, according to Google), so we'll stick with 700 mi^2 + Space for now.