Whatever Happened to the Man of Tomorrow is really good, but it's IMO dwarfed by All-Star Superman which tells a very similar story.
All-Star's got more polish (and physically more story, of course), but I dunno. That's a tough call.
I will list each one's advantages, because the Internet likes lists.
1. Lex Luthor's an actual character, who actually does things, instead of functioning as a life support system for Brainiac.
2. Nasthalthia Luthor's first appearance since antediluvian times.
3. The Professor Quintum = Luthor fan theory is pretty cool, although poorly supported by anything which actually occurs in the book.
4. Bar-El and Lilo are a better General Zod and Faora than General Zod and Faora. It's weird how these banana-flavored one-shotters probably brought more tears to my eyes than Superman's own sacrifice.
5. The death of Jonathan Kent is ultra-sad.
6. A huge variety of neat stuff that doesn't deserve their own bullet points, but are nonetheless cool to read.
7. Jimmy Olsen kicking the shit
out of Evil Superman.
7 1/2. Superman doesn't cry about justifiable homicide like a total wiener. However, this only counts one-half point, because you know he totally would
Whatever Happened to the Man of Tomorrow?
1. Brainiac is in it
, instead of being replaced by Morrison's pet idea Solaris. I dunno, man, I'd kind of expect the Tyrant Sun
to be bigger than, say, my house.
2. Bizarro's scene is short and tragic and beautiful, and not a two issue-long pounding headache.
3. Lois Lane is Lois Lane, and not a brown-haired misogynist stereotype who happens to share the same name.
4. The Legion of Super-Heroes are in it, instead of being replaced by Morrison's pet idea, the Council of Cross-Time Kangs. Yes, I forgot their name, because I do not care about Superman's grandkid having sex with a 5th-dimensional imp. Kryptonian sperm are vulnerable to magic, Grant. Be consistent!
5. The reaction to Supergirl's unexpected appearance is ultra-sad.
6. Lana Lang is rather bad-ass, if unfortunately somewhat easily defeated by the Legion of Super-Villains member who has his God Mode turned on.
7. That abomination Krypto dies.
8. Superman's (and Moore's) brutal deconstruction of Mxyzptlk, probably the most fearsome enemy he's ever faced.
7. Full point deducted for Superman's crybabying and self-flagellation with gold kryptonite, because he had to destroy an eldritch horror. However...
8 and 9. The wink! YES. DOUBLE-POINTS AWARDED.
Alan Moore wins! I declare him the best "No, I'm the Spiritual Kind of Magician, No I Can't Do Card Tricks--Do You Even Know Who I Am?" in comics.
I mean, no one wants to read about Hush, but I bet Paul Dini can at least do card tricks.