POW awarded it the greatest moment in comic book history, with the author stating that his only reservation was that it was a new moment (in the late 2000's) out of a medium that's been around for 80 plus years. The author also stated that it was the only choice to make.
If you took all eighty years of the character's history and distilled it into a single pure moment containing all his best qualities, that one page would be it. He inspires strength, wisdom, kindness, freedom, value and hope in just a few words. And he saves a life.
A moment that often gets left out of the discussion is the page preceding this one: Superman is talking to Lois, who got herself kidnapped by a mad scientist just so she could get his attention to talk to him, because she finally knows he's dying. Superman left her to come save this stranger. Because Superman's own happiness is nothing compared to the life of another person.
The end of the issue, as the Kandorians have failed to save him, Superman says that it doesn't matter and they'll do much better working with human cells, so he goes to the children's hospital and tells the kids he's got some friends for them to meet and they'll be going home soon.
A small moment, but when Clark Kent is lying on the floor of the Daily Planet, seemingly dead, Lex Luthor arrives and begins to threaten the occupants. While everyone else is standing up to Lex, Steve Lombard, a Jerk Jock sports writer who spent all his time bullying Clark is kneeling by him performing CPR.
Steve: Come on, Clark! You can do it, buddy! Come on!I'm sorry for all those times I played tricks on you.
The moment when the Kryptonian astronauts are lying, dying while Superman works through his options for saving them. They acknowledge the nobility Superman shows in trying to save two people who had spent the entire issue savaging everything he stands for and trying to beat him into submission. Superman points out he learned of mercy from his human parents.
Bar-El: Kal-El. I'm proud to call you my kin. Krypton's great heart lives on in you.
Earlier in the issue, Bar-El callously places the half-billion ton dwarf star key to the Fortress of Solitude in the hand of one of the robots, crushing it instantly: Superman immediately dashes to its side, placing a comforting hand on its shoulder as he retrieves the key.
In Issue 10, Superman creates an alternate Earth in a miniature universe so he can find out if a world could exist without a Superman. Even in Earth-Q, the sped-up history shows humanity at various stages of enlightenment championing the concept of a Superman. Leading up a moment one millisecond away in reality where a young man in Earth-Q's Cleveland is putting pencil to paper:
Joe Shuster: Third time's the charm... (panel reveals an early model of 1938 Superman) This is going to change everything...
The Superman Robots have a bit of a scene where they come to aide Superman to battle for the sun.
The presence of Lois Lane and Jimmy Olsen is a meta moment for their fans, given that Morrison left out certain elements as "important once, but not anymore." But these two are not among those elements.
Lex Luthor finally gets the one thing he wanted: Superman's powers (well that and Superman lying dead at his feet). But just as he's comprehending all the powers at Superman's disposal, those powers increase Luthor's awareness - perceiving the fragile and unique nature of reality itself - to where he understands why Superman is an ultimate force for Good.
Luthor (wide-eyed, mouth agape as tears begin to well up): It's so obvious. I can actually see and hear and feel and taste it and... The fundamental forces are all yoked by thought alone. It's thought-controlled! Hmm? Sorry... sorry, these new senses...I can actually see the machinery and wire connecting and separating everything since it all began... This is how he sees all the time, every day. Like, itís all just us, in here, together.And we're all we've got.
This is especially poignant if you adhere to the theory that Leo Quintum is actually a future version of Lex Luthor who reformed and dedicated his life to actually bettering the world after this moment of super-lucidity.
In the prison issue, after the Parasite has been dealt with, Lex to Clark and notes, with all sincerity, that he's always liked him, noting his decidedly human flaws and qualities as "everthing [Superman] isn't." Even when he insults Clark's clumsiness early on, he qualifies it by saying Clark writes like a poet. Adding in that this story takes most of its cues from the Silver Age, you can easily assume this Lex grew up in Smallville and has known Clark all his life. It's kind of heartwarming to know that even at his most cartoonishly supervillainous that Lex still has a sliver of humanity.
Superman: I only have moments to save the world. Lois: That's more than you ever needed. Superman: I love you, Lois Lane. Until the end of time.
The final lines of the animated film.
Quintum:(smiling) They always said they wanted children.
Lois:(echo) He's not dead. He's up there fixing the Sun. And when he's done, he'll be back.