So, What Makes Z-A a "LEGENDS" Pokémon Game Exactly...?

We've all heard about the new Pokémon game on the block; it's exciting to have another entry for the "Legends" branding, but that also raises that question, why DID they choose this game to follow in Arceus' footsteps? These games are really quite different, yet something about this new take on Lumiose City made it seem a worthy successor to the Legends title, but what exactly goes into a "Legends" game anyway? That's what we'll need to find out...