It truly is such a subjective thing. Obviously to give something 100% would be to imply it is absolutely perfect, which to me (once again opinion) is not possible or to imply as Eusis stated that the game achieved it's goal with no perceivable flaws. I would tend to stay away from the perfection idea and go with the idea of no, or little perceivable flaws. But even that is to an extent objective, for instance I think Fallout 3, Borderlands, Valkyria Chronicles, Nier, Persona 4 and Tales of the Abyss are simply the best games I have ever played, but obviously they all have flaws, however, I can overlook the flaws so to me they're probably as close to perfection as I rate anything.