I've only been playing KSP for a short while now, but I must say, its one hell of a game. Greatest game ever, no, not yet at least. I have always been a fan of games which reward the thinker, my highest game hours yet are on Silent Hunter 3 GWX and that's a hell of a game too, but neither will be the greatest game ever. The title of the greatest game ever has to go to something earth-shatteringly life changing, like COD! ...or any of the other 1 million iterations of similarly formatted, khaki-cladded banalities. Those are the games generations will talk about in the future, just as the classics of our generation are revered now, so will these titles. What really matters is whether 'you' think its the greatest game ever, because thats all that really matters in the end.