DC Animation recently released a double feature in their line of highly acclaimed animated films, Justice League: War and Justice League: The Flashpoint Paradox.
WARNING: Similar to the brilliant and highly recommended, Batman: Under the Red Hood, these films are for adults only. Parents should watch them before deciding if they're appropriate for their children.
The classic origin of the Justice League of America (JLA Vol 1, #9) brought Superman, Green Lantern, Aquaman, Wonder Woman, Flash, Batman and Martian Manhunter together to fight an invasion by aliens called the Appelliax (reference to this origin is made in the several episodes of the animated series Young Justice). The most recent revision of the DC universe, called The New 52, tweaks this story so that the invading force is from the hellish planet Apokolips, Martian Manhunter has been replaced by the pre-52 Teen Titan, Cyborg (aka: Victor Stone), and Shazam (aka: Captain Marvel/Billy Batson) is added to the line up. JL: War is the animated story of this new origin.