This should have been posted with the last post, but I wanted to check the facts with Rob before posting it...
Chris Anderson asked me to participate in giving a toast at the Wired Rave Awards dinner about why WoW was so great and giving a Raver award to Rob Pardo, Lead Game Designer of World of Warcraft (WoW), and his team. I had my own opinions about what made WoW so successful, but I asked Rob with whom I had the opportunity of sitting next to at the dinner. We had a longish conversation about games and WoW and was impressed by Rob's insights and practical experience.
Rob was a guild leader of a hardcore raiding guild on Everquest. Rob is a hardcore gamer. He loved the game, but realized that there were things that could be better designed. He looked at all of the MMOs and together with his team, built a game that was better in each of the different components than any of its competitors while keeping the core culture and functionality of MMOs. They added some important new features including the rest system, team PvP without segregating players from the opposing factions, and a completely quest driven experience, which were new innovations. They also paid attention to issues that existing games experienced or they anticipated would experience and designed WoW to deal with them.
For instance, WoW does not allow buying and selling game gold. However, according to Rob, it doesn't break the economy as some people think. The game is designed to minimize the negative impact of "farmers". The quests and and equipment are designed so that there are many key things that you can't buy with game gold. The issue of gold buying is primarily a matter of players feeling that it is unfair - the great thing about WoW and similar MMOs is that everyone starts equally regardless of what they do in real life.
Although Rob was a hardcore player in Everquest, he designed WoW so that it allowed casual players to have as much fun as hardcore players. It really shows and as a guild custodian of a guild that has many casual players, the ability for casual players to have fun in WoW is very important. Rob mentioned that one of they keys to success of a game is to make sure that the game is fun in the first 5 minutes. I think many game developers forget this and focus on gamers who are "serious" and willing to invest significant time to learn to play or wait a long time to have their first "fun event". I think it is the breadth and diversity of the players that Rob tried to appeal to that is the key to success of WoW and he did it through attention to detail and trying to get each part right rather than focus on a single killer feature.
It reminds me a bit of the book "From Good to Great".