First of all I must mention, that I am not a big fan of Clamp Arts, which is why I put off watching it until now. But since all the anime fan voices are praising it so much, I watched it anyway. And I was positively surprised: Not only was there a "double-hero" theme stretching throughout the whole story, but was the main focus on what you would normally call the "antagonist", a 17 year old boy, Leolouch, with a sad past, who seeks revenge and a better future for his sister, Nunnally, with an newly obtained power called "Geass".
His Geass enables him to force his will on others (when they look directly into his eyes), thus they will do as they are told, even if the order might be to kill them self. Moreover his intelligence and theoretic skills make him a master in planning intrigues and battle tactics, and he starts setting up a personal army, hiding his identity behind a mask and calling himself "Zero". Leading a double life as a school boy and on the other hand as the leader of a terrorist organisation, he tries to get back the autonomy of Japan, which has been stolen by his father, king of the so-called "Empire of Britannia". 
When his character was firstly introduced and the story started to evolve, I couldn´t help but think about Death Note and it´s maincharacter, Light. But after a few more episodes, it became obvious, that Code Geass was just a lot more superficial than Death Note, which I wouldn't say is a bad thing. It´s just that the setting, a future Japan with Battle Robots makes it a lot more difficult to have a "realistically calculating" character. But still it was sometimes really annoying how Lelouch could lead a battle led in the ocean with a map and a radio transmitter into victory....
On the other hand, we have Suzaku, former childhood friend of Lelouch, who joins the Britannia Army to change it from within.
The following plot develops as one could expect under those circumstances: Lelouch trying to hide his identity, intrigues, miraculous won battles, political problems etcetc. The kind of things, that make you wonder how everything is gonna turn out. But well then, I had my special highlight far too soon in the whole anime: When Euphemia (whom Suzaku serves as a knight and whos Lelouchs princess sister no. 20282- I dont really know, he has way too many siblings Oô) tries to create a special zone for Japanese people within the country, and all problems seem to been have solved, Lelouch makes the random mistake of using his Geass on her and commanding her to kill all the Japanese People, which end in a grand scale genocide.....well, I thought that was a bit to much for an unexpected turn-over, so I stopped watching for a while. xD I mean, come on, how stupid can you be, Lelouch....
And then everything came to an decisive battle between Zeros army, the "Black Knights" and the Britannia Empire, which was lost while Lelouch ended up being somewhere completely different and arguing with Suzaku. Each fired their gun at each other and puff, Season ended.
I was quite surprised, since the second season started with "1 year later", so I thought I accidentally skipped the last episode of season 1...but no. Lelouch had returned to living as a normal student, suddenly having a younger brother, and everyone seemed to have lost their memories. I was confused. After a while, Lelouch regains his memories and everything starts to make sense....In the end, I think it was an awesome way to start a new season, in complete confusion, and you only learn what happened a year before bit by bit.
Lelouch starts to lead a double life again, as a Lelouch who still has not his memories back and as Zero, commanding his Black Knights again against the Britannia Empire. Fast Skip forward: he ends up being able to kill the Emperor (who actually was immortal and tried to kill the gods- wft?!)....and then there are 4 episodes left, after a scene where, again, Suzaku and Lelouch have a showdown, but the outcome is unsure. 
At the beginning of the next episode, Lelouch reappears, with Suzaku at his side, declaring to the world that he will be the new Emperor. The last few episodes were the worst, really. I had no idea what was going on, or what he had planned. He conducts war against his last struggling brother, putting him under his Geass and taking his beloved Nunnally as a hostage... which was when I finally had no theories left of what he wanted to do. xD
(!!!!!!!!! WORST SPOILER EVER!~ so don´t read if you haven´t watched XD)
And then, final episode, he gets killed by a man masked like Zero, whos actually Suzaku....which was all planned to make Lelouch the "evil" that everyone projects their hatred on and to lead the world to peace....I must say, I don´t really see, how these things are connected, really, but well. It still was a worthy ending, somehow.
To sum it up, I think it was a great anime, although not one of the best I have ever seen. Sometimes, I was not even listening to the explanations and political-war talk anymore, because I was like "well yeah, whatever", and the fact that Lelouch had a harem of girls in love with him around him was quite an annoying fact aswell, but it was not too bad, as to stop midway. xD After a few episode, one gets easily captivated. Having a main-character with a basically good goal, approaching it by committing murder and crimes though, makes it quite epic. "All hail Rurusyu!" xD
