Interesting as WoW has been mentioned, because I think here - and please don't come at me with rope - I think Wizards should've followed WoW more.
When WoW came out, it didn't advertise anything new conceptually. You had the same races all the fans were used to, and the same places all the fans knew. Instead, they took the stuff they already had and used that to market to the outside crowd. Blizzard, in essence, used two different types of marketing to the two groups.
To the fans, Blizzard essentially said "Everything you love is here, and it's exactly how you've been loving it all this time." People ate it up in droves, and just about ever message board in existance was hit with "Oh man, I get to play an dwarf just like from the games!" or "Holy crap, I hope they go further in depth with tauren, I loved those guys from Warcraft 3!" Blizzard sold the old players the lore.
Then, to the new comers to Warcraft, they pimped - sorry for using the word, it hurts me to say it - out their gameplay. They talked aboutcasual gaming, and how their PVP system would cater to people who want to do it and don't want to do it. The new gamers weren't even close to being as interested in the lore as the old ones - the draw for new players is "This is fun to play."
That's where I think Wizards messed up. They did it backwards. They emphasized new mechanics for the old players who had, by now, simply houeruled whatever they wanted, and tried to make the new fluff WOWEE and XHARDXCOREX TO THE MAX for the new players. But the problem is, while I'm sure lots of new players like the fluff, that's not going to be what gets them into the game, and when you try to go out of your way to stand out and say LOOK AT ME I'M SKYDIVING WHILE CHUGGING GAME FUEL MASTER CHIEF EDITION, most of the new players will ignore you for the cover that has generic caucasian knight facing a dragon. Because new players aren't going to think "Gee, I want to find something new and exciting to dive into!" They're going to want something that's generic enough for them to be able to defend later when they're called a geek. And the more your game stands out, the geekier you are.