Grant Morrison keeps every preposterous idea from Superman's silly history, ditches any irony or nostalgia, folds it back in a way that it becomes awesome, and plunks it into a larger story fueled on pathos, genuine humor, and hope. This is the thing that comes after Post Modernism.
Some for instances-- there's no longer a ridiculous giant key to the Fortress of Solitude:
Or how about Zibarro, the bizarro Bizarro?:
Morrison also has the best and most sci-fi-ingly elegant answer ever for the question "How come we don't see Superman stopping Hitler/9-11/some other real world problem?" Which I don't think I can succinctly explain, let alone spoil, here.
The art is also, um, the best. Frank Quitely gets flak for drawing purse-lipped mush-faces, but his layouts and sense of space make up for it just a little. If I have a child, I am painting this on the nursery wall:
Perhaps you read something in the news today that made you feel ill about humanity. Well, All-Star Superman is something clever and good that might make you feel okay.