Every single piece of Avengers hyperbole you've heard is entirely accurate.
It's a ridiculously great spectacle, which if your name is not Chris Nolan is all you should be aiming to make when you helm a superhero movie. It draws from the best of Marvel traditions, with worlds colliding and massive battles and classic inter-squad squabbles. It benefits hugely from not having to be any kind of origin film: the only new element we hadn't seen in the previous installments of the Marvel filmiverse is the Chitauri, and you don't really need to explain their motivations or where they came from. They're just Loki's ugly evil invading force.
It also did something else though: it made me understand why people went apeshit over Superman in 1978.
Superman's never really connected with me for a couple of reasons, but the main one was that I didn't grow up reading DC comics. Sure, I knew who Supes and Bats and the rest were, but they weren't my scene as a kid. I made mine Marvel. And so, while so many other people were all "Oh wow, I never thought I'd ever see this on the big screen" with the Donner Superman, I was just kinda "Yeah, that's cool, I guess."
Avengers, far moreso than any other Marvel filmiverse entry to date, made me go "Oh wow, I never thought I'd ever see this on the big screen."
I'm not just talking about finally getting a version of the Hulk everyone can get behind. I'm talking about the real Marvel fanboy elements. We get to see the SHIELD Helicarrier!!! We get to see Hulk vs Thor and Thor vs Iron Man slugfests!!!! The obligatory Marvel post-film teaser contains fucking [spoiler redacted]!!!!!! Is it a perfect film? Of course not. Neither was Superman. But in every crucial way it's the big superhero team-up film I've always carried around in my head, and it's now escaped from my head.
And that's what makes it the second-most important superhero film ever after Superman. Just as Superman laid the groundwork for thirty years of superhero movies, suddenly Avengers has given us a template for the next thirty. Suddenly, there's hope for a Justice League movie. Suddenly, I'm actually glad that X-Men 3 fucked up the Phoenix Saga, because solid as Singer's set-up for it was in X2 there's now a way that it can be done properly in the inevitable next iteration of the team. Hell, suddenly really crazy stuff like the Secret Wars and [redacted; see redacted spoiler above] and a Teen Titans Trigon movie and, I dunno, a Valiant universe is on the table. Suddenly, the idea of a sprawling cosmic superhero epic isn't just a pipe dream. (And incidentally, the lack of ambition in that pathetic excuse for a Green Lantern movie looks even worse in comparison.)
In short, as they did in 1978, the rules just changed on what can be accomplished with superhero movies. Full credit to Marvel Studios and Joss Whedon for pulling off something that once upon a time I thought could never be done.
Now let's see who picks up that gauntlet...