[Aeran]

It's risky to make something too different. There is a reason a lot of games are so similar. When it comes to MMO games I believe it is also important to remember that they are abstractions of the real world, or some fictional world atleast. So naturally many things in them will be very similar. Together these games define a set of "tools" that can be used to create new games. E.g experience points of some kind seem to be used in many MMOs. Same with guilds, raids, and chat channels. Usually new MMOs introduce atleast something new to further the genre.

When it comes to excusing poor quality of a game I believe the issue might be mainly that they target such big audience. With the amount of content some of those games have it is amazing they has as high quality as they have. I've also noticed people tend to compare MMOs with the first MMO they played. Usually that first MMO just seem to get better and better each time they talk about it .