Fullmetal Alchemist, Koukyoushihen Eureka Seven Recommendations
Similar in telling a story that ends up on a much larger scale than it started! World and existential issues caught up in a coming-of-age type story. Both have lots of relatively complex minor characters. And both are frequently funny, while also tackling some deep stuff!
Both series are produced by the same anime studio, BONES, with roughly the same number of episodes each (50 E7/51 FMA). Both shows delve deep into their main characters pasts, and develop them nicely throughout their run. There are no cookie cutter characters to be found in either series, as each character is made out to be unique, with clear character designs for viewers to distinguish one character from another. They're also both fantasy adventures, with rules and powers unique to each series. The bgm/ost for both fit amazingly well for their respective series. If you're looking for something epic to watch, E7 & FMA
Both are around 50 or so episodes and are from Studio Bones. They both deal with the themes of intolerance, militarism and mass extermination carried out by said military. They also have a well developed cast of side characters.