I think KSP graphics are right on for the style that they want to convey. As you get closer to realistic graphics, you expect the gameplay to be more realistic like BF4 or COD. KSP is right in the sweet spot of looking good, but a little cartoony and colorful since that is the world Kerbals live in. As others have said, perhaps a little more polishing could be done, but I think the first time I got into space and saw the sunrise over Kerbin was just as breathtaking as the best scenes in more realistic looking games. That and there is something to be said for lower system requirements. I seem to be playing on my laptop a lot more, which is just using the integrated Intel Graphics 4000 on my i7-3540M CPU! Good luck with that on other games...