>>25013312Some people have suggested that Giratina and Arceus are loosely based off of Christianity, with Arceus being God and Giratina being Satan. Satan rules over Hell and the souls of the sinful dead. Because he's a ruler of ghosts and the dead, he can be loosely seen as a sort of dead king. This could be why Giratina is a ghost type.
Another reason for Giratina being a ghost type could be linked to ilthe distortion world. Pokedex entries state that the distortion world is the opposite of the Pokemon world. The Pokemon world could be seen as life and the distortion world could be seen as death. Since Giratina is the ruler of the distortion world, it would make sense tgat it's a ghost.
And just look at its design. It looks a hell of a lot more ghostly than Hoopa.