It’s a bit of a cliché: every time a new MMORPG is announced, it is promised to be a WoW-killer. And it never is. Unless SWTOR ends up being one but we can all agree that if it is it will e because of the power of the brand rather than the gameplay innovation.
Guild Wars 2 seems to be however genuine innovations worth looking at and summarized in that post. I particularly like the Skill-Based Action Combat: this has been a boring thing in WOW.
See on makeuseof.com