2. Main Characters Are Established Way In Advance
I deeply admired Marvels commitment to their cause. After the success of Iron Man, we saw several of their properties being developed for screen, some new (Thor for instance) some returning after years of absence (like Hulk and Captain America). Essentially, these movies served two purposes: to a) make money as stand-alone features and b) to establish the Avengers. Normally a movie requires you to establish each character separately and often this is the pitfall of an ensemble movie (see: Fantastic 4), but thanks to this slew of preluding films, the only character that needed to be established was The Avengers as a unit. You might be sceptical about the fact that Warner Bros. are looking to get their Justice League movie out in the next few years, that there isnt a long enough gestation period for them to establish everyone they need to ahead of time. But think about it: the two main members of the Justice League have already been established in the worlds consciousness over long, successful cinematic careers. Batman is one of the most popular comic book movie properties out there thanks in part to Nolans recent box-office destroyer, and Superman well, if you dont know what Supermans deal is, Ill have to assume that you yourself are alien to this planet. Ultimately, I reckon that everything else of importance could be established in the upcoming Man of Steel movie (which is rumoured to have been commandeered slightly by Warner Bros. for this very reason). Essentially, DC have already done the work for themselves by establishing their two main guys as some of the most well-known and well-loved superheroes of all time.