There are basically three things required to craft an Iron Man film: First, it should include Iron Man. Second, it should at least reference the major points and characters in the Iron Man mythos. Third--and I can't stress this enough--it shouldn't suck.
The worst thing about superhero movies is that they feel obliged to tell the hero's origin story, and this is usually dull and not relevant to the rest of the plot. Iron Man, though, is very cleverly plotted so that the origin story not only feeds into the rest of the movie; it doesn't exhaust its possibilities.
The film starts with billionaire industrialist Tony Stark taking a ride through Afghanistan to show off his company's new missile system. Sadly, they are attacked by some ideologically ill-defined Central Asian enemies, and Tony is taken hostage. In captivity, he meets Dr. Yinsen, who was also captured by the ideologically ill-defined Central Asian enemies, and the two of them are forced to build a missile for the warlord Raza.
In the old Iron Man comics, Dr. Yinsen was Chinese, and Tony Stark was captured by Southeast Asian communists, but times change, and now Dr. Yinsen is Afghani, and the enemies are a mix of Afghanis, Pakistanis, Arabs and, strangely, Hungarians. But the general thrust is the same: Tony Stark, who has become wealthy on weaponry, learns that weapons not only help people, but they also--surprisingly, and clearly in violation of their intended use--kill.
So instead of building Raza a missile, he creates a suit of armor so as to wreak bloody vengeance on his multiethnic oppressors. That part of the film is unexpectedly violent: Stark actually burns people alive, blows them up and then punches tiny holes in them and puts them in a three-ring binder and then closes the binder and hands it to his board of directors and says, "This report is filed!"
No, not the latter. But he does the other stuff with the burning and blowing up.
Anyway, the great thing about Iron Man is that the initial action sequence that sets up the origin story then turns out to be part of a much larger plot, which is part of a more general scheme, which is subsumed by a grand narrative. Throughout the film, everything gets explained, but without a lot of everyone's favorite movie scene--the scene in which people sit around and explain things. So that aspect of the film is not only competent; it's actually intelligent and well-thought-out.
Also successful are the actors, a surprisingly talented bunch. Robert Downey Jr. plays Tony Stark, and while Downey has been known to be occasionally hammy, here, it works for him, as Stark is sort of an overinflated blowhard whose only interests are getting inside machinery and women's underpants. But when Stark has his revelatory moment and discovers that some of the guns and bombs that he made have actually been used to wound puppies, Downey makes the transition smoothly without chewing the scenery, but also without going outside the bounds of good comic-book acting. In other words, he doesn't suddenly think he's making a Merchant/Ivory film.
The biggest surprise is the performance by Jeff Bridges as Stark's business partner, Obadiah Stane. Bridges really beefed up for the role and shaved his head, plus he towers over the diminutive Downey Jr., all of which work for him. But what's interesting is how well he plays the madcap bad guy. It's not the kind of thing he's done much of in the past, but he's a versatile actor, and he really nails the part.
Also very decent are the always-amusing Clark Gregg as government agent Phil Coulson, the surprisingly understated Gwyneth Paltrow as Tony's secretary, and Terrence Howard as Col. Jim Rhodes.
So the film has good plotting and acting, and also a really witty script which gets a good half-dozen laughs, and these weren't sympathy laughs. They were the kind of laughs that are caused by humor.
Now, for the nerdfolks of the world, Iron Man also has the following important elements: agents of S.H.I.E.L.D.; Stark's driver Happy Hogan and his secretary Pepper Potts; The Mandarin (sort of: There's an organization called "The Ten Rings," but it does the job); and favorite Iron villain the Iron Monger. But the really good news is that if nothing in this paragraph meant anything to you, it doesn't matter, because all of this is integrated seamlessly into the film so that both nerdpeople and full-length-pants-people can enjoy it.
In fact, this may be one of the most genuinely enjoyable films in some time. It's too smart to try to be deep, and it doesn't get bogged down in the usual sticky glue of origins and explanations that have derailed so many other superhero flicks. But most importantly, it knows exactly what is needed to make an entertaining action film without insulting the audience's intelligence. That's pretty hard to pull off, and while they don't give Academy Awards for this kind of technical excellence, if there were an Oscar for Best Attempt at Making a Superhero Film Without Thinking You're Some Hoity-Toity Artist and Also Without Thinking Your Audience Is Composed of Microcephalics, then I would nominate director Jon Favreau for that award.