Everything is a rip-off of everything.
There's no "innovation" possible anymore, every feature you see in games has already existed in a similar form earlier.
That's why I don't like patents, rip-off claims, and generally the word "innovation" in the whole IT industry. It's just stupid. What matters is the end result, not which features you copied where because it's almost impossible to bring out a new product WITHOUT building upon or copying stuff that has existed before, at least in form of a prototype or plan.
But that doesn't matter at all. What matters is the end result, the result of the whole package, how well it is done, how much and how well they integrated everything and how fun it is to play. WoW's ingredients are nowhere near innovative, but Blizzard uses them in such a way to create something of much higher quality and value than its competitors.