I, actually, disagree. I never found them to be similar series. I (sort of) see where people are coming from, with Light and Lelouch, but they both have very different personalities, and motives, overall.
Hm.. Well, I would recommend Mobile Suit Gundam SEED & it's sequel, Mobile Suit Gundam SEED Destiny, as it is from the same creators and has a similar set of characters / plot line.
I would also point you towards Shiki as well as Kuroshitsuji because, even though the plot / story is not all that similar to Code Geass's, quite a few characters Have traits ( physical and personality-wise) similar to that of Code Geass's.
And, even though this recommendation is quite the stretch, I would recommend trying out Mahou Shoujo Madoka Magica as well, if you enjoyed the emotional aspects of the series, as well as Season Two's finale.
(( Picture of Sunako Kirishiki from "Shiki" ))
posted over a year ago
For some reason, Mahou Shoujo Madoka Magika came to mind for me as well, though I agree, it's a stretch in terms of comparison. The magical system can be compared, since it's very much a double edged sword and it reflects who they are in some way, but I don't think the plot could be anymore different.
I'd shove in Pandora Hearts here. It's a very thoughtful show with a lot of things going on in the background and some major surprises. The magical system in use here is pretty different, using things called "chains," though it is a double-edged sword much like Geass. The characters are a little overly quirky, but it's still got some marked similarities.