In your example, the new rulers would kill all the animals and replace them with robots. It's better to be alive with hope then dead with none. In the Christian mind set, I'm sure Satan has his reasons and his followers their's but a satanic victory could hardly be perceived as good. I'm sure Satan would view his victory as good but that would hardly make it so. Some things aren't relative (sorry Einstein). They lost their freedom due to mistakes, poor judgement, poor character. They are gone and have been proven to be a catastrophe, even worse then the seven gods. Really, nearly all RPGs have an evil ending and a good ending (and sometimes, some in between) and the Godking/void wins ending is the nemesis of the whole game and would be a huge stretch of the imagination to call good to say the least.
Firstly, in mythology, Satan isn't the villain there : his creation and rebelling was just a part of amusing show of his creator - the God, who set all the rules, known what will happen, and still did it. Overall, character of the God, in the christian mythos, have selfish, infantile and egocentric personality, which is the reason of 90% his decisions, and which very similar to the character of Braccus Rex. At least, Seven Gods created mortal races in order to feed on their souls, so they could maintain their power, and not just to entertain themself by mortals like some kid with an ant farm. #satandidnothingwrong.
Secondly,God King and voidwoken, in their ending, do not genocide the races of Rivellon, like some "good" Lucian, but just enslave them. Still. isn't this better then be killed in Damian's invasion later on by some demons? Which also Lucian's fault. With God King in charge, Damian don't have even half of chance and there will be no more wars.
Worst possible ending, is to leave Lucian alive after all he's done. He should be the very first person to sacrifice in order to restore the vail between the Rivellon and the Void.