Ever heard of the words "Successful IP"?
How about WoW having a 15+ years of background in this universe? Blizzard + Warcraft = many people would buy/play this just because of that combination.
Ever heard of the fiasco called Diablo 3? Any idea why it sold 12 million (!!!) copies? Because of the IP. What does the number of sales have to do with the quality of the game? Nothing, the game sucks balls and that's admitted by a huge part of the community. Bye bye, Jay Wilson, anyone?
So can people please stop with the crap about numbers? Hell, RIFT probably has 0.5 mil subs and is still rocking their niche. WoW appeals to the mainstream community. Sad but true. Justin Bieber has the highest viewcount in Youtube. Do you listen to Justin Bieber and do those 500 mil views equal q uality music? Please....