Here are some old film projects that were started, but then dropped by Toho or another film company for some reason or another.
Why would they do such a thing? Read on!

The Volcano Monsters King Kong vs. Frankenstein Continuation: King Kong vs. Godzilla Frankenstein vs. The Human Vapor Frankenstein vs. Godzilla Mothra vs. Godzilla: Version One King Kong vs. Ebirah Frankenstein's Sons Batman vs. Godzilla All Monsters Attack Directive Godzilla vs. The Starfish Godzilla vs. Hedorah II Godzilla vs. Redmoon Godzilla vs. The Space Monsters The Return of King Ghidorah (1972) Gamera vs. Garasharp Godzilla vs. The Devil Godzilla vs. The Gargantua The Return of Godzilla: Version One Mothra vs. Bagan Godzilla vs. King Kong Godzilla vs. Mechani-Kong The Return of King Ghidorah (1992) Godzilla vs. Gigamoth Godzilla vs. MechaGodzilla II: Version One Godzilla vs. MechaGodzilla II: Version Two Godzilla vs. Ghost Godzilla Godzilla vs. Bagan Guilala vs. Gappa Godzilla vs. The Gryphon Godzilla vs. The Alien Monster Godzilla, Anguirus, Varan: Giant Monsters All-Out Attack