What does Loki, an all-powerful Asgardian with an entire alien army backing his play, have to fear from a mere mortal like Tony Stark?

"The Avengers," an arrogant-as-ever Tony offhandedly warns the villain just before the climax of the Marvel Studios superhero flick. "It's what we call ourselves: Earth's Mightiest Heroes."

But even if Thor's misguided brother has six heroes of varying sizes and power sets to fear, there's nothing for the folks at home to get nervous about: "Marvel's The Avengers" is an absolute masterpiece that fully sticks the landing. Written and directed by "Buffy the Vampire Slayer" creator Joss Whedon, "Avengers" takes six heroes who have zero business hanging out in the same movie — the aforementioned genius playboy Tony "Iron Man" Stark, man-out-of-time Steve "Captain America" Rogers, god-out-of-orbit Thor, hulking scientist Bruce Banner, and stone-cold spies Natasha "Black Widow" Romanoff and Clint "Hawkeye" Barton — and creates a cohesive whole that, against all odds, completely and utterly works.

Fans have been waiting since 2008's "Iron Man" — heck, since well before then — for "The Avengers" to hit theaters. Well, it's (almost) here, and it's as phenomenal as you'd hope it to be. Chances are you're already planning to see the biggest superhero assembly this side of Comic-Con, but in the rare event that you're not, here are five reasons to push you over the edge.

They Did It
That's the first thing you need to know: Somehow, some way, Whedon and the fine folks of Marvel Studios not only pulled off "The Avengers," they exceeded all expectations for just how great this movie can be. The idea of Iron Man and Thor sharing the same space onscreen wasn't always easy to swallow, but Whedon handles it fantastically, marrying all these characters together in a fully believable way through a compelling story and even greater dialogue and relationships. Some characters have more prominence than others, sure, but everyone gets their moment in the sun. It's a beautiful thing.

Kiss of the Spider
"Buffy," "Angel," "Dollhouse" and more — Whedon's greatest stories always feature incredibly powerful, fully realized heroines, and "Avengers" is no exception: This is the Black Widow you've all been waiting for. The filmmaker takes a one-note character from "Iron Man 2" and develops her into a crucial component to the success of "The Avengers." She kicks ass and doesn't bother taking names, but just as importantly, she cuts to the core of her surrounding teammates with ease. Her scenes with Hawkeye and Bruce Banner are particularly poignant, but it's her face-off with Loki that stands out as the highlight. Speaking of which ...

Master of Mischief
It's hard to top seeing Earth's mightiest heroes on the battlefield together. But if there's anything that comes close, it's Tom Hiddleston as Loki. He's the perfect choice for the "Avengers" villain: emotionally tied to the team, a deeply wounded individual who has a lot of anger issues to work out with mankind, a master of muddling even the greatest hero's thoughts. Hiddleston owned this role in "Thor," and he surpasses himself in "Avengers," thanks in large part to masterful writing from Whedon.

We Have a Hulk
Forget Loki's army, the good guys have exactly what they need: a mean, green giant with purple pants. (What, you don't have one of those?) I'm a proud fan of "The Incredible Hulk" and was sorry to see Edward Norton go, but if I'd known what Whedon and Mark Ruffalo had in store for Hulk fans, I wouldn't have complained even slightly about the recasting. Ruffalo is perfect as Bruce Banner, a world-weary scientist who has been through hell and back and is still around to tell the tale. As for the big green rage monster he transforms into from time to time? He's not only the coolest character in the flick; he's at the center of the movie's very best scene. Trailers have not spoiled this one, either. You'll know it when you see it.

Everyone's Having Fun
Don't get me wrong: I'm as excited for "The Dark Knight Rises" as anybody. But that movie is going to be bleak. You know it. I know it. Guess what "The Avengers" isn't? Bleak. It's the exact opposite. It's a bright burst of light shining through the modern tradition of gritty, salty, take-no-BS heroes that have populated theaters lately. Growly Batman and angsty Spider-Man have their place in the world, but there's so much to be said for a group of heroes that leave you hooting and hollering at just about every turn. More than anything, "The Avengers" is a fun time at the movies. That's as important as anything.

Check out everything we've got on "Marvel's The Avengers."

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