WARNING: Spoilers Follow
Judged as a single film Man of Steel is a success. But viewed as a first film of a franchise and cornerstone film of a new superhero universe, Man of Steel basically painted all follow-up films into a corner. The main reason is simple, where do they go from here?
While it took an entire team of superheroes and one human nuclear weapon to save the Earth from an alien invasion in the Marvel Universe, all the DC Universe required was Superman and one Kryptonian Phantom Zone “bomb”. And in reality, the threat level in Man of Steel was actually an Extinction-Level-Event. The aftermath in The Avengers was 9/11 level damage to the city and all the heroes being battered & bruised. InMan of Steel Metropolis suffers the equivalent of a nuclear detonation and Superman’s hair is not even tussled.
So, where do the filmmakers go from here? Who does Superman fight next? Who presents so large a threat that Superman would require help and need to form the Justice League?
The most logical answer to the Justice League question is Darkseid, ruler of the planet Apokolips. The problem with him is Thanos, who will most likely be the main villain of the second Avengers film. You will have two similar looking and powered villains–Thanos was inspired by Darkseid–fighting superhero teams with the fate of Earth/the Universe in the balance. And by the time of each films respective release we the audience will have a greater connection to the heroes in The Avengers.
As for the Superman question, who knows. If the filmmakers still do not want to use kryptonite as a weapon against the Man of Steel, then it is too soon for Lex Luthor to make an appearance as the main enemy. A possible option could be Brainiac, but would the filmmakers want to deal with Kandor in a bottle? By starting off the franchise with such a heavyweight enemy the filmmakers have limited their options of who would be a viable enemy for Superman to face.
Backtracking, the Nolan Batman films were never meant to create the DC Universe, and, more importantly, at the end of his trilogy Batman–the man and concept–no longer exist. That being said, Man of Steel is the first film of a new DC Universe, but it does not effectively setup a world in which other superheroes can plausibly exist. Where Marvel took their time to woo the audience into a world with heroes and slowly built that world to reveal their biggest gun, Thor; DC went straight for the biggest gun. The Hulk, Iron Man, and Captain America were all created by human technology, and Iron Man & Captain America were accepted as heroes in their time. In a world where heroes already existed and have great power & strength, Thor coming from the sky is plausible. But in Man of Steel Superman literally appeared out of the sky. The defeat of Zod’s forces is with the use of Superman’s alien technology. No evidence is given that humans are capable of producing any technology on par with Iron Man, or developing a serum or radiation that would create a Hulk. Nothing is presented to us to accept a world with Superman, Batman and Wonder Woman, let alone any of the other possible superheroes in the Justice League: Martian Man Hunter (alien), Hawkman (alien), Flash, Green Lantern, Aquaman, Cyborg.
If Snyder and Goyer only scaled back the method of Zod’s defeat it would have helped for at least the remainder of the Superman franchise. Remember that Kal-El only just became Superman. Until his fight with Zod and his forces he fought no one. His feats of strength and use of power were primarily to save people. How does Kal-El know how to fight? The film does present a plausible scenario of how an untrained Superman can defeat a Kryptonian soldier–crack their helmets and beat them while they are disoriented by their super-senses. But then the filmmakers remove it by having Zod quickly adapt to his new powers, and having a battle royal that levels most of Metropolis.
What could have, should have, but didn’t
What would I have done differently? In keeping with the no Kryptonite and Lex Luthor rule I would have made Metallo the main villain with a slightly reworked origin story. Instead of the cyborg being powered by kryptonite he could be powered by another radioactive meteorite. Metallo as a villain presents a world where humans are capable of advanced technology. Also, since one of Metallo’s ability is to convert other humans into cybernetic drones, he can create an army that Superman cannot defeat with strength for fear of killing the humans. Metallo can also use other metal and technology to augment his size and power. This enlarged Metallo can face and be defeated in a fight. By the end of this hypothetical movie Superman learns how to fight and wins, and Metropolis is not leveled.
From here the next Superman film could have the Intergang as the antagonist. Since they are supplied with technology and weapons from Apokolips they would have the means to challenge Superman, while setting up a big villain for a Justice League film. As for the first Justice League film, Zod and his cronies would have made great villains. Imagine a fight between Wonder Woman and Faora, the Martian Manhunter and Tor-An, and an underestimated Batman figuring out how to capture them all in the Phantom Zone. Though the setup of both my hypothetical Justice League films are similar to the Avengers films, in the first it is a limited number of superpowered aliens as opposed to a hoard, and in the second a few years would have passed since we saw Thanos in “Avengers 2”.
But all this is fantasy. In the end we are stuck with a Superman in full, and not one still trying to figure himself and his powers out. Whether the filmmakers can figure out a way to challenge Superman without loosing respect from the audience is an unknown. All I know is they made their job much more difficult by how they chose to end Man of Steel.