So far, all the superhero movies have been start-from-scratch, where the movie has to intoduce the hero, tell the origin story, set up a Big Bad to get the hero moving along the path to heroics, etc.
So each superhero movie has been more or less the same as all the rest - change the character, nudge the origin, different baddie - but overall, same formula.
But actual comic books don't do this (very often). When you buy a comic, you already know the hero's backstory - what you are getting is a story featuring that hero.
I postulate that with the superhero movies doing so well - and with so many characters having been introduced to the non-comic-reading public, that it will become possible to do stand-alone movies featuring known characters.
So you could do, for example, Arkham Aslyum (per the graphic novel) where the opening scene is Batman showing up at the front gate and meeting Gordon to be briefed on what is going on inside and why Batman is needed there - without having to show Batty's parents getting murdered, the discovery of the Batcave, the origin of the Batmobile etc etc.
You might have to do a couple of establishment scenes to show how this Batman differs from whatever movie came out last, but that's trivial compared to a full reboot.
DG