I've told people this so many times.
Batman and Spidermans origins can be told in like 10 minutes of a flashback sequence out of a 2 hour movie.
Batman is the easiest! Show him flashing back to that night in Crime Alley, his parents get shot (echo sound effects for emphasis). That's like 5 minutes. Then show him as a teen (because that's when it would have logically started) going through the beginning stages of trying to master all things (martial arts, criminal investigation, knowledge of firearms and weaponry, etc.) as a little montage of clips and scenes of the man growing up. Then bam...flash to modern day Gotham.
All of this could take like 10-15 minutes of a movie. I appreciated Batman Begins for showing that he spent madd time away from Gotham training but even BB did'nt truly do it justice.