I give Iron Man three and a half stars because it starts out very strong, but then slips in the second half. The one problem I have in the beginning is the non-linear element. It seems like ever since Pulp Fiction the non-linear element has been all the rage. The problem is Pulp Fiction had a purpose for the non-linear. Pulp Fiction is really several stories surrounding the same events. If there is only one story and no other rational reason for the non-linear, such as Memento, there is no reason for non-linear elements.
In any event, the first half of Iron Man is excellent. Tony Stark (Downey) is a weapons manufacturer who is kidnapped by terrorists, while in Afghanistan displaying the latest weapon from Stark Industries. Stark uses a prototype of the Iron Man suit to escape; however, when he returns to America he does not build the Iron Man suit to be a superhero. While imprisoned by the terrorists he notices all their weapons are from Stark Industries. Here a favorable and rational image of the arms manufacturer is depicted. Stark only developed weapons for the U.S. military so to be used to defend America and protect the lives of those who fight to defend America. His weapons are solely for protecting natural rights. Thus, he is disturbed when he notices the enemies, the violators of natural rights, have his weapons.
Consequently, he creates Iron Man to destroy his weapons that are in the hands of enemies. This is almost like Ayn Rand's hero Howard Roark who destroys his own building when the government builds it improperly. Also, Iron Man paints the rational depiction of the military. Iron Man is supposed to be one individual acting the way the military should act. Both are should only be concerned with protecting natural rights by destroying the violators.
Another strong element of Iron Man are the scenes when Stark builds the prototype and then creates the refined Iron Man. There are great scenes of Stark sweating and hammering in a cave with fire around him, and them more complicated assembly of the refined Iron Man. These sections adhere to the excellent tag line of the movie, "Heroes aren't born, they're made." Iron Man is basically praising the self-made man and the power of man. The superhero Iron Man is simply Stark, but he has a sophisticated vehicle to defend natural rights while protecting his own. Stark also needs his awesome mathematical and scientific abilities to create the suit. Thus, the message is man is a superhero because he has a sound morality and the reason to achieve greatness. Iron Man is basically a more technological version of Batman. However, Batman focuses more on the philosophical greatness of man, the moral angle, while Iron Man speaks to man's incredible ability to create and produce. Of course, both Batman and Iron Man praise reality and truth through Iron Man's emphasis on math and science and Batman's emphasis on philosophy.
Unfortunately, Iron Man begins to slip in the second half. Obadiah Stane (Bridges) is not well developed. His motives for creating the Iron Monger and trying to destroy Iron Man and kill Stark are vague. It appears he just wants to destroy and profit from destruction, but this is not incredibly clear and is really quite generic. However, Bridges does an excellent job as a villain.
Gwyneth Paltrow's acting as Virginia "Pepper" Pots also begins to slip in the second half. In the beginning Potts is intelligent and confident, but in the end the tone of her lines conveys the ditsy girl character.
I am also unsure about the last line of the film, but I am leaning towards liking it. In the end Stark admits to the press that he is Iron Man. As far as I know, the Iron Man comics did not have this angle. So that is what troubles me, not adhering to the Iron Man story line. I do understand adjustments must be made when changing from comic book to the silver screen, but this is a large deviation from the story as far as I can tell. However, this is the first superhero I know of that the individual has admitted to being a superhero, while still acting as the hero. This could develop some interesting superhero story lines never explored before.
Finally, I do like that S.H.I.E.L.D. is introduced in the movie, indicating that in future Iron Man flicks the government and Iron Man will have a strong connection. I have also heard rumors of a future Marvel superhero film of The Avengers, which is a team of superheroes including Iron Man, Captain America, Thor, and The Incredible Hulk, which will all have their own movies by then. I assume S.H.I.E.L.D. will also have a large role in this.