- Broken Base:
- The art is great. That's the only thing everyone agrees on. Man of Steel fans think it was a good story that streamlined the Superman universe and offered a fresh take on the lead character. MoS Detractors argue that Byrne didn't bring Superman back to basics at all but he turned the lead character into a whiny wimp, made Lex Luthor more one-dimensional than his Pre-Crisis self, and wrote off all he disliked (the Pre-Crisis rich Kryptonian lore, Supergirl, Superboy, Krypto, the Legion of Super-Heroes, the Fortress of Solitude...) causing long-term damage to the mythos. And there's a growing third camp that thinks Man of Steel was a good story in itself... but it shouldn't have been canon because it left the Superman universe very limited and irreversibly harmed the Superman's mythos and continuity in the long-term.
- This series introduced the idea that Clark Kent is "the real one", and that Superman doesn't really think of himself as being from Krypton (and Krypton was terrible anyway). This has resulted in two factions: one, which sees this as humanizing Superman and finally pulling him away from being an unrelateable god masquerading as a "weak" human and pining to be among his perfect brethren in a manner that makes sense, and the other, which sees it as nullifying Superman's biggest personal tragedy and sense of loneliness and wistfulness, offering the Family-Unfriendly Aesop of "immigrants should forget about their origins", and making Clark Kent much less endearing and fun in the process of giving him Superman's bravery. It's worth noting that pretty much every canon origin since then has gone back on this, depicting Krypton as a decent (if not perfect) culture which Superman is curious about, and Clark Kent as clumsy and nebbish to some degree.
- Reducing Superman's power, to the point of being battled by ordinary supervillains. Part of the fanbase argues it was completely necessary, as Superman's Bronze Age strength was so high that it amounted to a Story-Breaker Power, and it needed to be lowered to make conventional heroics possible. The other part argues that Superman should be the most powerful superhero around, as the Trope Maker, and making him fight regular supervillains rather than battling cosmic-scale threats or handling more thoughtful situations than ordinary brawls was wasting his potential. And a more old-school part says that Byrne didn't go far enough, and that he should have been brought to his Golden Age "can lift a car" status so he could feasibly beat up bankers and war profiteers again.
- Magnificent Bastard: This series pretty much defined the Magnificent Bastard Corrupt Corporate Executive Lex Luthor that would be his standard portrayal for years to come.
- Never Live It Down: Fans of the Legion of Super-Heroes have various feelings of annoyance about this title due to the fact that John Byrne omitted Superman's role as the Legion's inspiration by removing his career as Superboy. This book is the reason for the various, repeated attempts at continuity revisions to try and alter the Legion's backstory and its place in the DC Universe. It doesn't help Byrne admits he's hated the Legion since -literally- day one because they put Superboy through a Secret Test of Character:
Most folk 'round these parts know I have no fondness for the Legion. I was "present at conception", having read the story that introduced them when it was first published. My younger self — often the butt of cruel tricks played by the other kids at school — instantly hated these punks from the future for the trick they played on Superboy. My older self has never quite been able to get over it.
- Running the Asylum: John Byrne -a self-proclaimed Golden Age Superman fan- took advantage of his chance to rewrite the Superman universe by wiping out most of post-1949 additions to the mythos and replacing Superman's classic personality with George Reeves' interpretation which he happens to prefer.