It really is tremendous what Joss Whedon has done with the Avengers film.
Usually, when you have a lot of characters thrown together, there is a great chance it turns into a big cluster "u know what".
That didn't happen here and each super hero received enough screen time and relevance in the film.
It's practically unheard of.
If you look back on the X-Men franchise, a superhero film with a lot of characters, it was mainly all about Wolverine and to some extent the Charles Xavier/Eric Lensher relationship.
I really have no real qualms with the X-Men films because they were essentially the franchise that jump started the superhero film craze. (Credit to Blade films for techically really starting it, but X-Men boomed it to another level).
But looking back on the X-Men, Wolverine was no doubt the most popular and best character to focus on, but Cyclops, The Dark Phoenix....really got the shaft.
Avengers really didn't shaft any of the characters. And that is attributed to a great job by Whedon for his script and directing.