Okay for the Wiki contributor who was asking and anyone who is intrested, a list of downloadable anime for mazinger and related anime.
Great Mazinger (Incomplete)
Great Mazinger vs getter G
Mazinger z vs great general of D
Mazinger Z vs Devilman
Grendizer, Getter G, Great Maz vs Dragonsaurus
Devilman: The Birth/The Demon Bird/Apocalypse of Devilman
Getter Robo G