I like Luke because he's a complex hero. He takes the elements of a cookie cutter protagonist and mixes them up in interesting ways, while still hitting the major notes of a heroic character.
Luke is destined to be a hero from humble beginnings, yet that destiny includes the pull of the Dark Side. He has inherited not only his father's strength in the Force, but also his headstrong and rebellious nature, and his fateful ties to the heart of the battle for galactic liberty.
In his youth, Luke is a typical hero in many ways: daring, charismatic, capable -- and prone to rushing headlong into trouble, regardless of the risks. He does the right thing even if he has to charge into the lion's den, and quite often, that's exactly how he tries to solve his problems or fight a foe.
What gives Luke dimension as a hero is that his conflicts are personal and enduring. His relationship with power is a struggle against temptation; the seduction of the easy path to victory. All Luke has to do is let go of self-control and embrace his rage, and he can be unstoppable... at the cost of his principles and loyalties. It's his ties to his family and friends that hold him back from the brink.
Another reason I like Luke is that in his maturity he's not a "solved" character: he's a person. An impressive person, a respectable person, but a troubled person. He's burdened by the greatness of his name and the weight of grave failures that cut to the core of his worst impulses. And for a while he's all but crushed by shame and fear. It's hard to measure up to your own legend when you've always struggled with inner darkness.
But sure enough, like the hero he is, Luke finds strength and wisdom in the lessons of his past failures. He rallies, and makes his own legend come true, seizing victory and personal dignity with a sacrifice that spreads his story throughout the galaxy as the unquenchable spark of hope that fuels mass rebellion against tyranny.
Luke is a great character because he's not just a badass with a wit. He's also relatable, he's flawed, he embodies qualities that everyone can embrace to improve themselves. And finally, he's great because he achieves that greatness in a principled and selfless way that reflects the highest ideals of Jedi tradition. With his passing, his family's story comes full circle. He succeeds where his father failed, and then ascends to a higher station where he continues to witness and inspire younger generations in their own struggles to conquer their demons and build a better future.
