It's easy to joke about how the teaser trailer for The Avengers makes Joss Whedon's superhero ensemble look like another Iron Man movie, considering that Tony Stark (Robert Downey Jr.) got all the snappy lines and as much, if not more, screen-time than anyone else. Downey can dominate a scene like few others, so there's legitimate reason to be concerned that he might overshadow his peers in Whedon's film.
How then do you take Downey's charisma into account and prevent that from happening? Well, if you're Whedon, you simply let The Avengers be told from someone else's perspective.
Here is what Whedon told EW, about his approach to structuring the Avengers' narrative:
“I set out with a very simple problem: There is no reason for these people to be in the same movie. So that’s what my movie has to be about. So much of the movie takes place from Steve Rogers’ (Chris Evans) perspective, since he’s the guy who just woke up and sees this weird ass world. Everyone else has been living in it.”
That makes sense, all things considered. As mentioned before, Downey could end up being too much of a scene-stealer - by contrast, a character like Thor (Chris Hemsworth) is by his very nature less accessible, seeing how (in the Marvel movie universe, specifically) he's a semi-immortal extraterrestrial with almost incomprehensible physical abilities. Likewise, Bruce Banner/Hulk (Mark Ruffalo) is a brilliant scientist who has been living with his "condition" for long enough that the "weird ass world" presented in The Avengers shouldn't really leave him all that confounded.
Rogers/Captain America, on the other hand, is not only a true "average guy" who's been granted superpowers, but he's also a fish-out-of-water in The Avengers. His attempts to adjust to the modern-day world should make for one of the more captivating character arcs in the film. Rogers is an especially empathetic character and a good conduit for viewers who appreciate colorful personalities like Tony Stark's, but don't especially relate all that well (see: most everyone).
In conclusion: it sounds like a wise decision to let the film's events be "seen" through the eyes of Steve Rogers, on Whedon's part. One can only wonder if that aspect will be more heavily featured in the second Avengers trailer, which could be attached to prints of next month's Ghost Rider: Spirit of Vengeance - assuming it isn't released online earlier than that (*knock on wood*).
The Avengers will hit theaters around the U.S. on May 4th, 2012.