Goku originated from Manga and anime and then had video games made based on the animes. If the character didn't originate from a video game they can't be considered a video game character. We don't consider Spider-Man a movie or video game character because they made movies and games about him, we consider him a comicbook character because thats where he was first created.
At least thats my reasoning for why Goku's a anime/Manga character and can't be considered a video game character.