Films like “Superman II,” “Spider-Man,” and “Batman Begins” proved that comic book icons can come alive on the big screen in intelligent, commercially successful ways. But for every triumph, there are any number of failed or simply mediocre adaptations — “Daredevil,” “Fantasic Four,” “The Hulk.” And I’d rather not even mention such monstrosities as “Superman IV: The Quest for Peace” or “Batman and Robin,” possibly the worst big studio movie ever made.

OK, I didn’t need the “possibly.”

So is “Iron Man,” the first big popcorn movie of 2008, a triumph or a tragedy? A stud or a dud? A pick or a pan?

I’m happy to say the Jon Favreau-helmed blockbuster belongs among the top tier of super-hero movies. It is enormously entertaining and likely to satisfy fanboys and Iron Man novices alike.

“Iron Man” is based on the popular Marvel Comics character first introduced in 1963. While not as well-known as fellow Marvel characters like Spidey and the Hulk (who gets a second chance in a big screen adaptation this summer), he has long been a fan favorite.

The plot of the movie stays largely faithul to the comic book story: Billionaire weapons manufacturer Tony Stark (Downey ), is captured by terrorists in Afghanistan and ordered to build them a missile. Instead Stark, who is a brilliant inventor, constructs a powered exoskeleton to escape. Back in the states, Stark perfects the suit and becomes Iron Man.

Why does the movie work? Let’s start with the cast, which is among the more accomplished ever put together for a comic book flick. Paltrow and Bridges are Oscar winners, while Downey and Howard have been nominated.

Downey really is the key to the movie. Stark is one of the more interesting alter egos in the super hero world. Pre-Iron Man, he is essentially a war profiteer, a notorious womanizer and a shallow celebrity. He is likable, but hardly admirable (he also is an alcoholic, something only touched on in the film, but a theme I suspect will be further explored in sequels).

Downey, with his own well-know problems with substance abuse problems and often tabloid lifestyle, proves remarkably adapt at taking on the Stark role. His ability to make Stark believable, as well as the humor be he brings to the film, set it apart from many action films, where character development is essentially irrelevant.

Speaking of action, there’s plenty of it: All the explosions and fight scenes you would expect, plus the requisite climatic battle scene. But Favreau (“Elf”) is fairly restrained. Many action films, frankly, overdo the action, with lots of redundant, seemingly endless fight scenes. “Iron Man” doesn’t fall into that trap.

The special effects are exceptional as well, with none of the obvious CGI-ness of, say, “The Hulk” or any of the “Star Wars” prequels.

“Iron Man” is the first of a planned trilogy. Let’s hope Favreau can sustain a high standard through three films. As the Superman, Batman (and to a lesser extent Spider-Man) franchises have proved, the third movie often is where things start to go off the rails.