This is what happened before the original trilogy in my mind:
EPISODE I
The old republic is shaking on its foundation. The jedi knights are still guarding the galaxy on orders of the senate but the citizens are losing faith in the order when more and more terrorist attacks hits the society. The rumors are a sith lord is rising and stands behind the attacks...
The moderate leaders of the senate are losing ground, and more radical elements are gaining power, which leads to state of emergency and temporary laws that loosen the rule of law. Among other things, a clone army of jedis is created to guard the republic.
The king of Alderaan has been leading a fraction of the clone army attacking a terrorist nest where they managed to save a young slave girl that claims she has information regarding who's behind the attacks. On their way back to Alderaan they're being attacked and the girl is being kidnapped. The king turns to his adjutant, Obi Wan, and orders him to find the slave before she is killed.
Obi Wan travels to Tatooine where he is robbed by a teenage boy that uses the force to cheat people out of their belongings. After a chase Obi Wan catches the boy and persuades him to be his guide. The boy, Anakin, takes him to his family that tells Obi Wan that the boy is an orphin they adopted, but having trouble controlling. Obi Wan starts to take a liking to Anakin who is kind of likeble rascal.
Anakin presents Obi Wan to his friends, a small rough gang of different aliens, and after some adventures they manage to sneak into the terrorist lair and find the girl. They also find an old bearded man in a robe. Obi Wan immediately falls on his knees, greeting the old man calling him "Master Kenobi". It turns out Obi Wan is not a jedi knight, he is a clone warrior with the serial number OB-1 and the old man is the original jedi he was cloned from. They all manage to escape and the slave girl tells them that she has heard that the terrorist attacks is an inside job and that they can trust no one. She also tells her saviors about the next terrorist attack which will be directed at the senate head quarters.
Meanwhile, the senate is out serching for OB-1, regarding him as a threat since they haven't heard from him and believe he might have deserted or become a ronin. Anakin, OB-1, Master Kenobi and the slave returns to Alderaan to stop the attack and manages to do so despite they're being attacked by both sides. Master Kenobi is struck down in a battle with a sith warrior and dies in the arms of OB-1 telling him he has proven he is not just a copy but a man who can makes his own choices. OB-1 cries and calls him father.
The senate is safe for now and our heroes are being honored with a ceremony where OB-1 is going to be dubbed a jedi knight by the new secretary general of the rebublic. OB-1 approaches the throne and kneels before it. A man in a black robe is sitting in the throne, and when we here his voice we immediately recognize it:
Palpatine: Rise, Jedi knight.
End Credit