Straight to TV

[The Giant Pacific Octopus]

[Xenorama]

i think these are all correct, except MAJIN which was released to theaters, perhaps only subbed and in limited release. i'm also not convinced that MAJIN STRIKES AGAIN was ever dubbed or released here- no one i know has seen it.
THE WAR IN SPACE was also a direct to tv movie. The Last Dinosaur was only released in tv here- it was a made for tv movie. not sure about THE THREE TREASURES at all though. THE MAGIC SERPENT was also a tv only release. add The Bermuda Depths and Toho's Drac movies and ESPY as tv only (i think).
naturally, there will be more people that can add to your list with great certainty.
David

Attack Of The Mushroom People (Matango)
Godzilla VS The Sea Monster
Son Of Godzilla
The Three Treasures
Dagora The Space Monster
All Gamera films excluding GAMERA THE INVINCIBLE
The Diamajin Trilogy (Majin Monster of Terror, Return of the Giant Majin and Majin Strikes Again)
Warning From Space
Monster from a Prehistoric Planet
The X From Outer Space
Legend Of Dinosaurs
Terror Beneath The Sea
The Last Dinosaur
Yongary Monster from The Deep (Korean)

[The Giant Pacific Octopus]

[Stargodzilla]

[musukogoji]