I've made some observations over the years on the themes of the Star Wars Saga. Basically each movie in the Original Trilogy had a different theme that was common in many of the character's story.
Episode IV A New Hope: this was a story about self sacrifice, and tragic loss. Obiwan Kenobi sacrificed his life for the greater good. Leia lost her home planet, but not allowing the Empire to discover the hidden base. Han gave up repaying Jabba the Hutt, and returning to his way of life, in order to help his friends in a life or death battle. Luke pretty much lost everything. His home, his friends, family and mentor. It left him no choice but to pursue a higher purpose.
Episode V The Empire Strikes Back was a story confronting your past. Vader confronted his past through Luke, his son, who was wreaking havoc on the Empire. Han was confronted by his past through Boba fett, claiming bounty for defaulting on his debt to Jabba. Lando was confronted by his long time buddy Han bringing the Empire to his hidden city. Luke was confronted by his father, destroying everything he thought he knew.
Episode VI Return Of The Jedi was a story of redemption or death. Those who were redeemed were transformed those who refused died. Jabba, fett, the Emperor all died for being over confident and arrogant. The others were redeemed in some way. Obviously Vader was redeemed and even though he died, he was transformed into a force spirit. Even C-3PO was transformed from a servant to a god. Remember in ANH he told Luke he wasn't good at telling stories, but in ROTJ it was his great story telling that convinced the Ewoks to fight against the Empire, which ended up being the game changer in the battle over good and evil. Leia was transformed from cold and crass, to being a warm hearted nurturer. Lando was redeemed from having betrayed his friend and a collaborating with the Empire, to saving his friends life, and later becoming a big player in the destruction of the Empire. Han was transformed from a carbonite frozen scoundrel to a hero. He volunteered for a dangerous mission and eventually settled down. Lastly Luke was finally transformed into a Jedi Knight.
I really think these were the themes that made the OT such a great story. Those are just the main underlying themes for each movie. They're probably common knowledge, but that's what I've noticed recently. There are many more, so if you'd like please add your own observations on any of the Star wars episodes.