“The Avengers,” which opened Friday, is poised to become one of the year’s top three commercial flicks, threatening to set records. We think it’s one of the best comic-book movies ever. Here is why (caution, mild spoilers ahead):

1. “THE AVENGERS” fleshes out each superhero — and our villain — smartly.

Everything about Joss Whedon’s film is on point — even going so far as to pay homage to the original first issue of the comic from 1963, which featured Loki (Tom Hiddleston) as the main villain (just like the movie).

Among the Avengers, Captain America struggles to adapt to life 70 years past his present, as well as to the edgy sense of humor of Iron Man. Bruce Banner’s big brain is needed, even though the doc’s not interested in letting the Hulk out of his mental cage. The Black Widow is dealing with her own personal issues and Thor must accept that he has to help take down adopted brother Loki for the sake of Earth.

Even when the skin is gamma-green, characters are fleshed-out with white-hot intelligence.

2. BLACK WIDOW holds her own: It would be easy for Scarlet Johansson’s Black Widow — who doesn’t have powers quite like the rest — to be lost in this big-boys-with-toys club. But Scarlett’s Black Widow stares down the Hulk and Loki — her powers of persuasion are sometimes the strongest talent of all.

3. IRON MAN’s new suit tricks: With all the nifty flying maneuvers and impressive weapons, we forget Iron Man’s high-tech suit also makes him very strong. In “Avengers,” he easily goes blow to blow with Thor.

4. THOR’s hairy conflicts: The Hulk and Thor duke it out in spectacular fashion.

5. THE STARK snark: What’s better than Iron Man’s maneuvers? Tony Stark’s quick-quips, verbally thrusting and parrying. Robert Downey Jr. doesn’t need the super-suit to light up the screen.

6. THE HULK as “smash!” hit: Enter Hulk, up-stage right. New addition Mark Ruffalo is winning as a thoughtful Bruce Banner — the best big-screen Dr. Banner so far, superior to the gifted Ed Norton and Eric Bana — but his CGI alter-ego steals entire scenes. Verdict: Hulk like Whedon!

7. THE EXQUISITE build: By the time we get to the Avengers forming a circle on that blasted-out Manhattan avenue, the film has built to the finale beautifully.

Verdict: Whedon knows crescendo!