If you're looking for anime similar to Code Geass: Lelouch of the Rebellion, you might like these titles. All recommendations are made by Anime-Planet users like you!
Ten years before Shirou Emiya's and Saber's fateful meeting, Japan is the stage for the fourth Holy Grail War. Seven Masters, each with his own dreams, step forward to win the boon of the mystic relic. Into this fray comes Kiritsugu Emiya, the enigmatic "Mage Killer" who wants to use the Grail to make a better world. Can he, paired with the indomitable Saber win the War? Or will he fall to the ambitions of the other mages?
Both of these series involve loads of chracters making intricate plans against each other for various motivations. There is action and a supernatural element in both. Code Geass has a lot of high school age characters while Fate/Zero mostly involves adults, and there are more not-so-serious episodes in Code Geass. Code Geass has mechs while Fate/Zero has swords and sorcery. But they both have more plotting and gambits than you can count. If you like that aspect of one, you'll almost certainly like the other.
Hakaze, princess of the Kusaribe mage clan, has been betrayed and marooned on an island by her own people. They seek to revive the Tree of Exodus, an incomprehensibly powerful entity of alien origin, to save the world from the tyranny of its antithesis: the Tree of Genesis that powers their magic. Hakaze, however, believes their efforts put humanity in jeopardy; and with her power limited, she can only reach out to the world to beg for aid. Her call reaches Mahiro Fuwa, a young man grieving the mysterious death of his sister, Aika. He and his friend Yoshino agree to help - on the condition that Hakaze track down Aika's killer with her magic. The deal is made, and the battle that will determine civilization's fate is begun: but who will play the part of its villain, and who its savior?
They're both great animes with dark themes where the protagonists fight to right an injustice and an almost brother/rival relationship between the two male characters. They have complex characters where motivations are not always clear cut and events can turn the story on its head.
The characters are also similarly somewhat haughty and arrogant (CG - Lelouch, ZnT - Shakespear quoting lolita complex guy) anti heroes. I liked Geass a bit better due to its length but Tempest has a much more satisfying ending imo. Enjoyable animes both.
Fifteen-year-old Ichigo Kurosaki is a typical teen with fighting skills, two caring sisters and a special trait: he can see ghosts. However, when Ichigo and his family find themselves under attack by a huge beast, Ichigo discovers that there’s more to the supernatural world than the everyday specter. Vengeful spirits known as Hollows roam the world in search of devouring souls, and Shinigami – soul reapers – work tirelessly to defeat them and guide normal ghosts into a place called Soul Society. Ichigo valiantly fights the Hollow that threatens his sisters, but on the verge of defeat a Shinigami named Rukia gives him her powers, turning him into a Shinigami himself. Ichigo must now adjust to his new life of both vanquishing and saving souls for the sake of Soul Society.
Show may be different due to it's differences but the main Characters Lelouch and Suzaku's ideals and friendship are similar to Yuri and Flynn where Lelouch and Yuri wants to change from the outside and Suzaku and Flynn wants to change within. Both are awesome where it involves battles, politics, corruption, drama, blood, loss of allies, and friendship.
After defeating the evil Chaos, Syaoran and the gang have arrived in what appears to be an apocalyptic and run-down Tokyo – a city in which acid rain has destroyed the buildings and taken numerous lives. The atmosphere is ripe with tension, as the city’s remaining survivors have formed clans in hopes of protecting the underground wells from other clans and strangers alike – strangers like Syaoran and friends. With Sakura’s remaining feathers being located in the wells and opposition at every turn, the feathers’ retrieval seems dire, and Syaoran will finally face his most dangerous enemy...
Code Geass and Tsubasa: Tokyo Revelations are similar in someway whereas the main setting Japan which Tokyo is part of is in a desperate state (Japan is colonized in Code Geass and Tokyo is in ruins in Tsubasa: Tokyo Revelations) as groups such as the Black Knights and Kamui's and Fuma's respective parties search for a way to restore their homes back to normal. Lelouch's character design is similar to Kamui and Suzaku's to Syaoran due to Clamp doing both the character designs. Twists and betrayal occurs as well as revelations that will change the story forever. Both shows have dark tone and action packed fights as well though they are different in terms of style (Code Geass-Mecha and Tsubasa-Magic). Try watching one of these if you've watched one of them which will be a great addition to your collection!