Dark Knight Returns is one of the most overrated comics of all time, and it really doesn't age well. The best thing about the book, and the part that does hold up is the way Frank Miller lays out and composes the story, and unfortunately that's the kind of thing that doesn't translate to another medium. The other part that made it so huge is translatable to other mediums, but it's also the grim-dark, angry, hateful Batman in a grim-dark, corrupt, and depressing world that's been seen many, many times since.