The key to those games is to set your own goals. It may not be an alternative that you want to play, but it is a very viable alternative and can be quite challenging. Personally, I have a couple of things in mind that are more in the middle grounds. The theme park style of WoW is high maintenance for little reward, I don't think it's feasible to continue going down that road for new games. The full sandbox mode is probably not the perfect solution either.