I totally have to disagree with that. WoW became successful through great marketing and availability (low system requirements). That combined with ongoing updates and content helped a lot. Some of the innovations credited to Blizzard were in fact player innovations. For example quest tracking was originally an addon built by a player, Blizzard later adapted that as part of the game.
In terms of content, the o3 (Original 3, UO, EQ, and AC) offered a much better experience. To this day any MMO I see is filtered through my AC experience and AC has essentially spoiled me.
Most 2nd and 3rd generation MMO's were greatly "dumbed down" in order to appeal to a larger audience and hence be able to earn more money. This trend started, sadly, with AC2 (one of the first 2nd gen MMO's) when Microsoft got her claws embedded in the project. How did gamers react?... Well today AC1 is still out and AC2 has long since been cancelled so it didn't work, AC still attracts gamers that want freedom and challenge. But for the most part, MMO developers of other games are making it easier on players and that kills the game for me. In another example, Earth & Beyond was cancelled due to trailing interest in the game. How is that a older game made it while a newer game like E&B didn't? E&B lacked content and thought pretty graphics was all players *really* cared about, it also had *no* PvP. And this was during a time when there were not as many MMO's to choose from (2004).
A good looking game attracts attention, but it's longevity is based on content, and if you have both....
So what was that unique - unheard - unseen of - content WoW came up with?