And those 20 years worth of games combined probably dont come close to the amount of palyers wow has and had.
Ofcourse, a modern game ecplises a 15 year old one (in its core) in many basic features, but the complexity of wow is on another level.
Unless you're working on a next gen mmorpg (that will actually be released so star citizen doesnt count LOL), i dont think you can compare the game you are working on with wow.