These are all the Godzilla characters in alphabetic order:

A:

Albino Gyaos

Anguirus (Showa)

Anguirus (Millenium)

Aqua Mothra

Armored Mothra

B:

Baby Godzilla

Bagan (Non-used)

Baragon (Showa)

Baragon (Millenium)

Baruagon

Battra

Battra Larva

Biollonte (Rose Form)

Biollante (Final Form)

Burning Godzilla

C:

Cretaceous King Ghidorah

D:

Dagahra (Dagarla)

Death Ghidorah (Des-Ghidorah) (Land Form)

Death Ghidorah (Flying Form)

Destoroyah (Mirco Form)

Destoroyah (Juvenile Form)

Destoroyah (Aggregate Form)

Destoroyah (Flying Form)

Destoroyah (Final Form)

Dorats

E:

Ebirah

Eternal Mothra

F:

Fake Godzilla (Mechagodzilla)

Fairy (Rebirth Of Mothra series)

Fairy Mothra

Fire Rodan

Frankenstein

G:

Gabara

Gamera (Showa)

Gamera (Heisei; 1995-1997))

Gamera (Heisei/Millenium; 1999))

Gamera (Millenium; 2006)

Garu-Garu (Rebirth of Mothra series)

Garu-Garu II

Garu-Garu III

Giara

Ghidrah (Showa)

Ghidorah (Millenium)

Gigamoth (Non-used; Heisei)

Gigamoth (Comic book exclusive; Millenium)

Gigan (Showa)

Gigan (Millenium)

Gigan (Upgraded; Millenium)

Godzilla (Showa)

Godzilla (Heisei)

Godzilla Jr. (Heisei)

Godzilla Jr. (Millenium)

Godzillasaurus

Gojira

Gorosaurus

Grand (King) Ghidorah (Rebirth of Mothra series)

Gurion

Gyaos (Showa)

Gyaos (Heisei; 1995)

Gyaos (Millenium)

H:

Hedorah (Showa)

Hedorah (Millenium)

Hyper Gamera (Heisei; 1999)

Hyper Gyaos (Heisei; 1999)

I:

Irys (Juvenile)

Irys

J:

Jet Jaguar

Jiger

K:

Kamacuras (Showa)

Kamacuras (Millenium)

Kamoebas (Showa)

Kamoebas (Millenium)

Kasier Ghidorah

King Ceasar (Showa)

King Ceasar (Millenium)

King Ghidorah (Showa)

King Ghidorah (Heisei)

King Ghidorah (Millenium)

King Kong

Kiryu

Kumonga (Showa)

Kumonga (Millenium)

L:

Legion (Soilder)

Legion (Plant)

Legion

Light Speed Mothra

Little Godzilla

M:

Maguma

Manda (Showa)

Manda (Millenium)

Mecha-King Ghidorah

Mechagodzilla (Showa)

Mechagodzilla 2 (Showa)

Mechagodzilla II (Heisei)

Mechani-Kong (Showa)

Meganulon (Showa)

Meganulon (Millenium)

Meganula

Megaguirus

Millennian

Minilla (Showa)

Minilla (Millenium)

Moguera (Showa)

M.O.G.U.E.R.A. (Moguera 2) (Heisei)

Monster X

Mothra (Showa)

Mothra Larva (Showa)

Mothra (Heisei)

Mothra (Heisei; Rebirth of Mothra series)

Mothra Larva (Heisei)

Mothra (GMK; Millenium)

Mothra Larva (GMK; Millenium)

Mothra (Millenium)

Mothra Larva (Millenium)

Mothra Leo (Rebirth of Mothra series)

Mothra Leo Larva (Rebirth of Mothra series)

O:

Orga

Orochi (Showa)

Orochi (Heisei)

Orochi (Millenium)

P:

Primitive Mothra (Rebirth of Mothra series)

R:

Rainbow Mothra (Mothra Leo)

Rodan (Showa)

Rodan (Heisei)

Rodan (Millenium)

S:

Sanda

Shockirus

SpaceGodzilla (Normal Form)

SpaceGodzilla (Flying Form)

Space Gyaos

Super Gyaos

Super Mechagodzilla (Mechagodzilla II)

T:

Titanosaurus (Showa)

Titanosaurus (Non-used; Heisei)

Titanosaurus (Non-used; Millenium)

Toto (Gamera) (Millenuim)

V:

Varan

Viras

Z:

Zedus

Zigra

Zilla