First off here is the timeline as promised..
Batman Begins (2010)
The Dark Knight (2011)
Green Lantern (2012)
The Man of Steel (2012)
The Caped Crusader (2012)
The Flash (2013)
Wonder Woman (2013)
Justice League (2014)
NOTES
Here is an advanced sypnosis because I know lots of people would be put off with a full movie script or a full destriction of every scene.. First off though we need a recap of what has happened in the movies leading up to Justice League..
CAST
Christian Bale as Bruce Wayne/Batman
Henry Cavill as Kal-El/Clark Kent/Superman
Emily Blunt as Princess Diana/Wonder Woman
Ryan Reynolds as Hal Jordan/Green Lantern
Djinson Honsou as J'onn J'onzz/John Jones/Martian Manhunter
Chris Pine as Wally West/Flash
Phil Winchester as Orin/Arthur Curry/Aquaman
Mickey Rouke (voice) as Darkseid
Judi Dench as Granny Goodness
Glen Jacobs as Kalibak
Morgan Freeman as Lucius Fox
Angela Bassett as Amanda Waller
Ralph Fiennes as Lex Luthor
Sam Elliott as Gen. Samuel Lane
Gary Oldman as Com. James Gordon
Michael Caine as Alfred Pennyworth
Olivia Wilde as Lois Lane
Anton Yelchin as Jimmy Olsen
SYPNOSIS: Darkseid sends his son Kalibak across the stars in search of Brainiac, the android that attacked his homeworld so that Darkseid can defeat him. Arriving on earth, Kalibak finds traces of Brainiac all over earth in computers before being confronted by Batman and Superman. Kalibak retreats and says that earth is protecting Brainiac so Darkseid mounts a full scale attack on Earth. When Boom Tubes open all over Earth attacking the cities, heroes across the globe begin to engage the alien forces. Mysterious alien J'onn J'onzz tracks down earth's strongest heroes to form a team strong enough to defeat the aliens and the mighty Darkseid, the Justice League. With other heroes around the world individually fighting the thousands of Para-Demons, Superman, Batman, Wonder Woman, Green Lantern, Flash, Martian Manhunter and Aquaman try and find a way to shut down Darkseid's power for his forces. As they split up, Superman and Batman go to the Batcave to work on a way to find Darkseid, Aquaman begins to dsetroy the many power plants placed in the sea, Wonder Woman and Martian Manhunter go to confront Granny Goodness while Flash and Green Lantern go to stop Kalibak. As the team do their missions, Batman along with Lucius Fox manage to create a bomb out of the tech Kalibak left on earth and go to confront Darkseid on his mother ship. As Wonder Woman and Martian Manhunter destroy all of Granny's para-demons, she retriets to Darkseid's side, as does Kalibak who is defeated by Flash and Green Lantern. Superman and Batman go to the mothership where Superman confronts Darkseid toe to toe in a brutal battle while Batman evades the para-demons to place the bomb. Darkseid calls all his troops to destroy the Justice League, as Wonder Woman, Green Lantern and Martian Manhunter engage Darkseid along with Superman. Flash helps Batman speed past the para demons. Aquaman has finally destroyed all the sea power plants leaving Darkseid's forces without their protective shields, leaving them vulnerable where the world's armed forces destroy them. As Darkseid fights most of the League, he is defeated and told never to return to earth. They flee the ship, but Superman returns and opens up a Boom Tube before leaving. Darkseid then realises there is a bomb aboard before smiling. His mother ship explodes in a nuclear blast in the sky above America as his minions are defeated by armed forces around the world. The Justice League are honoured by the US president as saviors of earth, where they announce they will always be.
STORY NOTES
Superman 2 will feature Brainiac coming to Earth after defeating Metallo and Parasite in The Man of Steel. Brainiac has been searching for the Crystal of Knowledge that is attached to Kal-El's ship buried beneath the Kent Farm. Whilst searching for it, he attacked Apokolips, home of Darkseid.. and is therefore set before Justice League but will be released after it.
There is cameos by James Gordon, Alfred, Lucius Fox, Lois Lane, Jimmy Olsen, Lex Luthor, Sam Lane and Amanda Waller. Gordon is present at Wayne Enterprises just as Det. John Jones is leaving. In reality, Martian Manhunter used his telepathy to make everybody believe he was in charge so he could get the alien tech from Lucius Fox. Lois Lane and Jimmy Olsen cameo when Superman as Clark Kent hears the whining Batman creates and also reporting on the alien invasion. Sam Lane, Waller and Luthor all cameo leading Earth's forces against the aliens.
J'onn J'onzz actually is the main founder of the JL, recruiting everybody but Superman takes the leadership role of the League.
When the Justice League are presented with an honour, Batman and Aquaman are not present which Superman acknowledges. He also says that the Justice League is not just 7 people in costumes, but every hero in the world, every police officer and firman etc.
There is also cameos by the following heroes: Green Arrow, Black Canary, Hawkman, Hawkgirl, Captain Atom.