In watching each series I saw a great many similarities between the two. They're both about high school-aged boys who are given a great power and use it to change the world. Both Light and Lelouch are extremely intelligent, and both are forced to live double lives to achieve their goals. However I believe that I can prove Lelouch was the hero of his tale, while Light was the villain.
Quick recap time! Death Note is about a boy, Light, who finds a tool of the gods - a Death Note is a book that shinigami (death gods, grim reapers) keep. Writing a person's name in the book causes that person to die. One shinigami, Ryuk, got bored and decided to let his notebook fall into the hands of a human, just to see what happens. Light uses its power to kill criminals because he believes the world will be a better place without them. Code Geass is about another boy, Lelouch, who was the prince of a great nation but after his mother is murdered, his power-obsessed father the Emperor exiles him and his younger sister Nunnally. Nunnally was crippled in the attack on their mother and blinded by the trauma of the incident, so Lelouch must care for her. He is later granted a power called Geass - which manifests in different ways for different people, in his case he can order anyone to do exactly what he says, but only once per person - and decides to use this power to bring down his tyrant father and his corrupt nation.
Without sitting here and telling you the entire story behind each anime, I can tell you that while each boy's incredible mind is a great asset, their intelligence also backs them into corners from time to time. While the majority of their victims are deserving of their fate, there are plenty of innocent bystanders who are caught up and killed in the great battles as well, because there was no other choice. Here is the greatest difference between Light and Lelouch - the longer Light's campaign for good went on, the more self-serving he became. He eventually began to see himself as supreme, unbeatable, the new God. As such, he believed all of his actions were good and right, and never felt bad about any of the things he did, no matter how twisted or how many suffered. Lelouch on the other hand, although one of his motives was revenge for his mother's death, he also recognized that his father's ambition toward total world domination was wrong, and above all he wanted the world to be safe for his little sister. When Lelouch made mistakes, although they may have been for the greater good, he felt great remorse for those who died needlessly. No matter how far he took things, and how much power he wielded himself, he never lost the ability to feel guilt.
Another similarity that has a different outcome? Both Light and Lelouch are killed at the end of their series. Their deaths are vastly different - Lelouch planned his, probably knew all along that it would need to happen anyway; Light never expected to get caught, so his final confrontation was a surprise that he could not accept, up until the very end. But more importantly, after their deaths, only Lelouch's goal was realized. Without Light and his version of justice in the form of the Death Note, the world did not change much. While he was alive, and sort of a boogeyman for would-be criminals, bad things happened less; but after he was gone and proved to be a normal person, evil-doers everywhere went back to doing evil because now they had no fear of retribution. After all that Lelouch and his rebellion had done, his death only cemented the peoples' belief that things needed to change. His father is gone now as well, and so the nation cannot stop the rest of the world from restoring peace and balance.
Now, you wanna know why Lelouch's plan worked out and Light's failed? Because although Light started with good intentions, he lost sight of the greater good and was only doing things for himself. He stopped caring about others and only cared about himself. His motives were selfish, and that was his downfall. Alternatively, everything Lelouch did was for his little sister, Nunnally. None of the battles he fought were for himself. He was willing to give his own life in the end to ensure peace whereas Light was not. This is why Lelouch succeeded.
So, I think you can tell who I'd pick for the winner of this showdown. I wanna know of you all agree or disagree, and tell me why. One of my favorite things about the anime fan community is sharing our detailed theories, so please speak up!
This week's post is over, but we still have two more rounds of Showdown September to go. Don't miss out! I'll see you all again soon!