Making a game unique is sure to make it also shortlived because for as many games that are unique there are 10's or hundreds that copy it, and then it isn't unique anymore. Being unique is temporary and fashionable. It comes and goes. You should be looking for longevity and consistent depth that makes the game transcend time and be something people will want to keep playing, regardless of what else comes along. If you don't protect yourself against the next new greatest thing, in that way, your product is going to disappear under a pile of rubble.