No secret identities; empowered women; lame villains (except Loki!); more tell-tale signs
Iron Man was the first proper Marvel Studios production: The first Marvel superhero film that was self-financed by the company, and the first film in the unlikely Avengers mega-franchise. The 2008 film retroactively reads like a statement of purpose for the studio and that's especially true in the closing moments. Robert Downey Jr.'s Tony Stark attempts to read an official statement, claiming that the metal-headed superhero is actually his bodyguard. (The ''bodyguard'' explanation worked for decades in the comic books.) But besieged by the media and maybe already growing bored of the deception, Stark simply states, ''I am Iron Man.''
The Secret Identity is a concept rooted in superhero lore, but it doesn't really exist in the Marvel Cinematic Universe. The Thor comics long employed variations on the idea that Thor was tied to a human alter ego; on screen, Thor is just Thor. Captain America's mask is a propaganda tool, quickly discarded. This sets the Marvel Studios films apart from the DC films and Sony's Spider-Man series, where tensions often run high in the heroes' double life.
You could argue that removing the secret identities makes the heroes less emotionally complex: Because they're always superheroes, there's a weird strain of workaholism running through the films, a sense that the characters have no real inner life. (What does Black Widow do when she's not Black Widow?) But the lack of secret identity anxiety gives the films a tone very distinctive from Sony's recurrent Spider-Man saga or the DC films.