Superman is a complex character, as superheroes go, too complicated to reduce into hero stereotypes and character-bio shorthands. He is Clark Kent, farm boy from Kansas; he is Superman, hero of Metropolis and symbol of Freedom, Justice, and The American Way; and he is Kal-El, alien from Krypton, his parents killed and homeland destroyed. And the most interesting, human moments experienced by Superman always show up in the interplay between his coexistent identities.
But in Zach Snyder's Man Of Steel, Superman (Henry Cavill, best known for his work on The Tudors) is there mostly to satiate that part of the American psyche that wants their messiahs to punch things, too. It's understandable why Snyder, director of stylish, brooding action movies like 300 and Watchmen, chose to go this route: the film is packed densely with information and plot, covering the death of planet Krypton, Clark Kent's upbringing in Kansas, his antagonists and their objectives, and the myriad twists and turns that result.
The hand of Christopher Nolan (who shares a story credit) is clear here—anyone who sat through The Dark Knight or Inception will recognize Nolan's proclivity for stories with climaxes that go on for half an hour. So amid all the action scenes, flashbacks, and cutaways that follow around Lois Lane (a precedent-breaking redhead, Amy Adams) as she investigates into who exactly this superhuman person is, there simply wasn't room to earnestly explore Superman's identity issues.
Unfortunately, the movie's climax still depends on Superman feeling torn between his respective roles, human/alien/messiah, all of them in some way true and all of them impossible to entirely fulfill. But we almost never have a good handle on why Clark does the things that he does, on how his identity motivates his actions. And when we are given reasons, they aren't very believable.
Clark returns to Kansas after discovering the details of his origins and says to his mother, "I know where I'm from, and who I am." It's a moment that takes the true-if-overwrought moments— a young Clark pleading with his father, "Can't I just be your son?"—and radically simplifies them. What at first seemed to hint that there's a burgeoning tension in Clark's psyche are now just moments of weakness, and Superman's strength within the movie isn't found in embracing his inherent personality pastiche, but in rejecting it.
"I'm an American through and through," announces Superman at the end of the movie, but he didn't have to go very far to get there. Superman's father, Jor-El (or more accurately a holographic program of his personality, portrayed by Russell Crowe) explicitly rejects the plans for earth harbored by evil general Zod (played to cold militaristic perfection by the always-terrifying Michael Shannon), and that turns Zod's character from a genuine moral threat for Superman into a Balkanesque nationalist who will sacrifice anything for the sake of his homeland—and thus, into someone we have no fear of Superman coming to resemble.