From Atlantic Refuge:Also, Frank Miller's opus is considered an 'else-worlds' story - it's not an official part of DC continuity. The only way he had Batman beat him was by having him cheat and use Kryptonite.
I never found Superman interesting until Miller presented him as a bureaucratic stooge in Dark Knight Returns. There he was a fascinatingly conflicted character: a hero with a shameful side, a superpowered Faust who has made a pact with the government and who learns that in every bargain with the Devil you find yourself acting less and less in your interest and more and more in his. It's probably the most insightful idea ever wrung out of the man, and, to be fair, one of the better ideas ever wrung out of Miller. Maybe Supes' noblest moment was, not necessarily when his ass was being kicked, but when he hung his head in shame at what he'd done, or allowed to be done.