Since 2008 and the release of "Iron Man," which featured a post-credits tag involving Samuel L. Jackson as a shadowy government figure who spoke of a larger, more unknowable world, the Marvel Cinematic Universe had been picking up steam. Each movie linked up with the previous film (or the next one), through subtle undercurrents and more overt connections. And it all came together with "The Avengers," which was released five years ago (time flies when Thor does, too). Joss Whedon's film saw superheroes Iron Man (Robert Downey Jr.), Black Widow (Scarlett Johansson), Captain America (Chris Evans), Thor (Chris Hemsworth), Hawkeye (Jeremy Renner), and The Hulk (Mark Ruffalo) come together to fight Thor's power-hungry brother Loki (Tom Hiddleston) and a band of rampaging extraterrestrials. It kicked ass. And it still kicks ass, all these years later.

In fact, I'd argue that it's still the best superhero movie ever.

Below are the nine ways that "The Avengers" set itself apart from every superhero movie before it (and since), and why it remains, all these years later, the cream of the proverbial crop.

1. Nobody Had Ever Seen Anything Like It

We take superhero team-up movies for granted nowadays. Last year's "Captain America: Civil War," a supposedly stand-alone "Captain America" movie, had more superheroes than the second "Avengers" movie, for crying out loud. But at the time, this was fairly unprecedented territory. Nobody had seen something, with multiple heroes, all played by huge stars, sharing the screen time, in a movie that was the summation of several other films, stretched across several years. It could have been a huge disaster. Instead, it was transcendent. I still remember seeing the movie about a month before it was released, at a screening that was coordinated by a radio station, in New York City. It was 10 a.m. on a Saturday, and I remember the tears welling up in my eyes because there really were things in the movie that, as a lifelong comics fan, I never thought I'd see in a movie. But it was all there and it was totally brilliant.

2. It Followed Through on All That Promise

There were unreasonable expectations associated with this movie, considering that, for the previous half-decade, breadcrumbs had been left throughout every other Marvel Studios movie about where things were headed. We knew that the superheroes would, eventually, meet up, and they would have to face something that was so catastrophic that it required all of their considerable might. Beyond those details we didn't know much what to expect (which, again, is helpful because it was such a wonderful surprise). But one thing was sure: it had to be good. Otherwise, all of the goodwill and promise that had been built by those previous films would have been squandered and the rest of the Marvel Cinematic Universe, which had already been mapped out for years (if not decades) in advance, would have potentially crumbled. But "The Avengers" did the impossible: It made good on all that promise and remains a cornerstone of the entire Marvel Cinematic Universe a half-decade later.

3. The Heroes Were Flawed (But Not Overwhelmingly So)

Looking back on this first film, it's interesting to see how much the heroes fight each other. (This was years before "Captain America: Civil War" would turn this concept into an entire epic movie.) And it's true that each of these heroes carried around a certain amount of baggage, emotional and otherwise, that needed to be addressed, dealt with, and then compartmentalized (at least long enough to fight that alien horde). But where "The Avengers" really succeeded and where some superhero movies in recent years have gotten stuck, is that it didn't dwell on the psychic trauma of our heroes. It admitted that they were flawed, and took the necessary time to address those flaws, but it never felt bogged down by it. There is a certain amount of psychological imbalance to prompt someone to don a cape and jumpsuit and face-off against a demigod and Whedon was wise to acknowledge that. The characters were complicated but (crucially) never a drag.

4. It's So Joss Whedon

Hundreds of people were responsible for "The Avengers," from the talented folks fixing Scarlett's wig to the countless digital artists who brought the Hulk to brilliant life. The fact that there's any kind of authorial stamp on this movie seems like a miracle. But this movie is, through and through, the work of writer-director Joss Whedon (who returned, under significantly more strained circumstances, for the busy sequel "Avengers: Age of Ultron"). Anyone who saw it earlier television output (things like "Buffy the Vampire Slayer" and "Firefly") could see it from moment one. It's a hoot to hear his characteristic ratatat dialogue come out of the mouths of a tech billionaire, living demigod, and twitchy scientist, all at the same time, and his nimble handling of multiple characters and storylines, swiftly culminating in a grand climax, should be applauded, studied, and adhered to (this is how you do it, kids). Without Whedon's deft handling of the material, we would have probably not had the two "Guardians of the Galaxy" movies (both written and directed by James Gunn). It proved that a filmmaker could really put their stamp on one of these movies, even within the giant machine.

5. Everyone Had Their Moment

There are a ton of characters in this movie, and yet they each have a satisfying arc, and are allowed signature moments, both in quieter, talky scenes and the big action set pieces (more on those in a minute). It's pretty shocking, considering how many themes, ideas, and storylines there are that any of the characters has a moment to themselves. But it's true. Each hero gets his or her time to shine. Even Hawkeye, who fairly early on in the movie is relegated to a pseudo-bad guy, comes back in the last act to really cement himself as a member of the team (and a key asset to the larger Marvel Cinematic Universe).

6. It Set the Stage for What Was to Come

And speaking of the larger Marvel Cinematic Universe, a few seconds in the middle of "The Avengers"' credits would set the stage for the next "phase" of the movies. It was then that we were introduced to Thanos, the mad titan and the big bad who has been looming over every movie since "The Avengers." (If he hasn't made an appearance outright then the Infinity Stones, the mystical doodads that would grant him domain over the entire universe, certainly have.) It was a gutsy move, and what could have just been a throwaway gag has been instrumental in shaping the contours of the Marvel Cinematic Universe for the next half-decade. It also gave rise to superhero movies that were, after the runaway success of something as different as "The Avengers," willing to take chances and get weird. Without "The Avengers," it's doubtful we would have had movies as unique as "Guardians of the Galaxy," "Doctor Strange," or "Ant-Man." Very importantly, it set precedence that all are welcome in the Marvel Cinematic Universe.

7. It Reminded People That These Movies Are Based on Comic Books

In recent years, a lot of superhero movies have been very serious. "The Dark Knight," another brilliant superhero exploration and the movie that most would point to as the best comic book movie ever, also functions as a critique of Bush-era politics and the dangerous of a runaway surveillance state. Um ... fun? "The Avengers" was deeply funny and colorful and reminded people that, while we might be living in the age of the graphic novel, that these characters came from comic books. It's right there in the name. Whedon knows better than anybody that you can have real stakes and still get some good zingers in there.

"Marvel's The Avengers" ..Thor (Chris Hemsworth) and Black Widow (Scarlett Johansson)..Ph: Film Frame..� 2011 MVLFFLLC. TM & � 2011 Marvel.  All Rights Reserved.8. There Was Real Emotion

That's the other thing about "The Avengers" that is often overlooked; this movie has a lot of heart. It's a warm superhero movie. And when Agent Coulson (Clark Gregg), whose original appearances in the MCU was more of a gag than anything else, goes to the big heli-carrier in the sky, you really feel it. That's a big moment, both for the audience and the characters. (Forget that it was all undone, almost immediately, when he was mystifyingly resurrected and planet at the head of ABC's long-running "Agents of S.H.I.E.L.D." television series.) These were characters who fought and screamed and punched each other but they also felt, quite deeply, and formed their own dysfunctional family unit during the course of the movie. ("Family" is a big theme for Whedon and pops up again and again in his work.) Many superhero movies nowadays are defined by how chilly they are, both production-design-wise and emotionally. But "The Avengers" proved that its heart could be as big as its rippling biceps.

9. Those Set Pieces Though

It's easy to applaud the headier, more artistic dimensions that make "The Avengers" so special, the more visceral elements of the movie need to be championed as well. Which brings us to ... the set pieces. There aren't that many set pieces in "The Avengers," just a handful, but they do the job spectacularly well. And the climactic assault on New York City is arguably the greatest superhero action sequence in the history of the medium. There's so much to love about that sequence, from the tiny character details to the swirling camera to the fact that, while the action is scattered across large swaths of midtown Manhattan (and that it was shot in both New York City and Cleveland), the spatial relationships of the characters and the geography of the attack is very clearly defined and reinforced, time after time. There are moments of shaky-cam intensity but most of it is smooth and clear. That's saying something. And let's not forget about things like the classic 360 shot that loops around the characters (still the coolest shot, like, ever) and the moment where Bruce Banner reveals that he's always angry. These are the moments that made me (and countless viewers) squeal with childish glee. And they're the moments that contribute to "The Avengers" being the greatest superhero movie ever.