Total Recommendations: 4
Both are space operas featuring giant mechas. Like in Gundam Seed, an invasion takes place in the first episode of Valvrave, forcing the protagonist to pilot an overpowered mecha to fight off his enemies.
They are both extremely stylistic mecha series involving a supernatural twist and an alternate history setting. Like Code Geass, Valvrave utilises a number of well-known anime tropes, including a high school setting, and the various character types are nothing unique. But the way these different elements come together - and the way some ludicrous plot twists are revealed - give both anime series a distinct charm.
Both feature a cynical guy jaded about love who is forced to join a school club. Both play with the standard high school love comedy tropes and feature witty dialogue and a sassy female lead.