MMO Clones... Where to start? lets see, got my notes, soapbox and foot ready to put in my mouth so here we go.
I don't think any game company wants to have their game ripped apart and told its just another WoW clone or copy of some other game but really that's what gaming has been since its conception. Game companies grasping onto others ideas and trying to either improve them or just create their own alternative.
Remember Wolfenstein, Doom, Quake, Half-life, Unreal. Were they really all that different from one another? Not really imho but they kept improving upon an earlier idea. Just look at Bioshock, I mean wow have fps games come a long way.
How about RTS games. When Warcraft first released we played it like crazy. Then Warcraft 2 came out and so did all the clones but some of them are great franchises still today. Age of Empires, Command and Conquer. All a little different but for all intents and purpose just Warcraft clones.
I would think MMO's are no different. The player base finds certain mechanics in a game that it likes and scream if they are not in their next game. How is a developer suppose to deviate from the path when customers freak out if they even change the color? I think the changes have to be more content related rather than mechanics. You don't have to reinvent Blizzards wheel which in reality they just took from all the other MMO's. Just realize that it can be improved upon and create content accordingly. Vanguard tried a new wheel... now maybe they should of made sure it had actual air in it before rolling it out to the public but they tried. At best I believe Vanguard will just be a niche game, not the juggernaut they wanted. There really is room for a lot of different MMO's, companies just have to be content with smaller subs and not keep looking over at blizzards lawn. CCP seems to be doing fine using this attitude.
Fantasy novels aren't all clones.. well some are but in general they're not. Sure most have Elves, dwarves etc but the stories are what make them different. They don't read from back to front just to make it different. Why should games be different? Give people a cool place to play and they will play there. You don't need to paint your monkey-bars a different color, just put up a hot-dog stand for the parents and they'll bring their kids to your playground instead of the other empty one. ( Yeah that was a weird analogy but hey my coffee cup is empty ).