SAN DIEGO — Captain America: The First Avenger might be the ultimate revenge-of-the-nerd fantasy. Filled with enough runt jokes to sink a battleship, the World War II superhero flick expertly maps one little guy’s chemically enhanced transformation into a burly supersoldier.

Steve Rogers, the pipsqueak with a purpose, is played by Chris Evans. Injected with a secret serum and juiced with Vita-Rays, the patriotic weakling morphs into a buff commando with a straight-arrow attitude.

The actor introduced the movie at its world premiere Thursday during a screening packed with fans, most if not all lured to San Diego by the siren call of Comic-Con International. After a short performance by a chorus line of beauties dressed in red, white and blue sequined outfits — their high kicks elicited shouts of “God bless America!” from some in attendance — Evans shilled for the movie, which sets him up to take a principle place in the Marvel Studios film universe.

“To me, this is everything a superhero movie should be,” Evans said.

(Spoiler alert: Minor plot points follow.)

And so it is, to a point. The PG-13 Captain America, which opens Friday, delivers the goods on many fronts: charismatic leading actor, enticing love interest, plenty of action and an effective tie-in to Marvel’s coming superhero team-up movie, The Avengers (due in 2012, but let’s just say you should stick around till after the Captain America credits if you’re interested in a sneak peek).

But the standard hero’s journey, when applied to a sickly wannabe soldier who would gladly lay down his life to serve his country, makes this comic book origin story all the more satisfying. You can see in Evans’ earnest portrayal — his head digitally grafted onto the scrawny body of a five-time 4-F reject who yearns to fight Nazis — the not-so-quiet desperation of a young man who hears the call to action but cannot answer.

It’s like a vintage Charles Atlas ad, pumped up into a two-hour blitz of action, comedy, World War II nostalgia and freakish sci-fi military technology. Director Joe Johnston truly redeems himself after soiling the sheets with 2010 horror flop The Wolfman.

While Captain America might be formulaic, it’s a winning formula that Marvel has hit upon with Iron Man and Thor. This latest superhero movie on the road to The Avengers is certainly energetic and filled with geeky eye candy. The massive tanks, warplanes and weird weapons cooked up by renegade Nazi scientist Johann Schmidt (played by Hugo Weaving) and his Hydra faction look truly impressive on the screen, mixing ’40s-era profiles with lasers for a retro-futuristic feel.

Weaving’s heavily accented performance, part Agent Smith and part Schwarzenegger, might be less formidable than you would expect from the talented actor as he portrays Schmidt, aka the Red Skull. But Tommy Lee Jones, as a roughneck colonel who at first thinks feeble recruit Steve Rogers isn’t up to the task, brings plenty of firepower to the war story. Much like the Warriors Three in Thor, Cap’s comic book allies — Dum Dum Dugan and the rest — get short shrift in the film, serving mainly as fanboy window dressing.

Hayley Atwell, as Peggy Carter, a hotshot agent who bonds with Steve Rogers before he becomes the star-spangled Avenger, hits all the right notes as a take-no-guff tough gal who would make any red-blooded guy want to enlist.

Evans himself? He’s surprisingly soulful as the skinny kid who bears the brunt of so many wisecracks. Scenes during the young fighter’s boot-camp hell prove particularly poignant. And he’s convincingly beefy and sober (literally) as the no-nonsense hero with the nearly indestructible Vibranium shield.

Before the screening, Evans must have felt slightly meta when he found himself whipping up the crowd, just as he did playing the newly transformed Steve Rogers in the movie. (Captain America initially gets assigned to do a song-and-dance fundraising tour to encourage support for the Allied effort through sales of war bonds.)

Touting the world premiere, the actor might as well have been hanging propaganda posters that said, “Loose lips sell tix.”

“If you like it, tell people,” Evans said. Judging by the raucous applause at the movie’s end (and again after the Avengers tag), and by the comments of the throngs exiting the theater, gushing about the movie and making plans to see it again with friends, it looks like Marvel’s supersoldier will soon be receiving a 21-gun salute at the box office.

Attention, Comic-Con: Mission accomplished.