Here is a list of all the original classic GODZILLA films, it consists of three segments:

Segment 1:
#1 GODZILLA: KING OF THE MONSTERS
#2 GODZILLA RAIDS AGAIN
Segment 2:
#3 KING KONG VS. GODZILLA
#4 MOTHRA VS. GODZILLA
#5 GHIDORAH: THE THREE HEADED MONSTER
#6 INVASION OF ASTRO-MONSTER
#7 GODZILLA VS. THE SEA MONSTER
#8 SON OF GODZILLA
#9 DESTROY ALL MONSTERS
#10 GODZILLA'S REVENGE
Segment 3
#11 GODZILLA VS. HEDORAH
#12 GODZILLA VS. GIGAN
#13 GODZILLA VS. MEGALON
#14 GODZILLA VS. MECHAGODZILLA
#15 TERROR OF MECHAGODZILLA
This is a list of the second series:
#16 GODZILLA 1985
#17 GODZILLA VS. BIOLLANTE
#18 GODZILLA VS. KING GHIDORAH
#19 GODZILLA & MOTHRA: THE BATTLE FOR EARTH
#20 GODZILLA VS. MECHAGODZILLA II
#21 GODZILLA VS. SPACE GODZILLA
#22 GODZILLA VS. DESTOROYAH
This is the third series:
#23 GODZILLA (1998)
#24 GODZILLA 2000
#25 GODZILLA VS. MEGAGUIRAS
#26 GODZILLA, MOTHRA & KING GHIDORAH: GIANT MONSTERS ALL-OUT ATTACK
#27 GODZILLA AGAINST MECHAGODZILLA
#28 GODZILLA: TOKYO S.O.S.
#29 GODZILLA: FINAL WARS
This is the first GAMERA series:
#1 GAMMERA THE INVINCIBLE
#2 WAR OF THE MONSTERS
#3 RETURN OF THE GIANT MONSTERS
#4 DESTROY ALL MONSTERS
#5 ATTACK OF THE MONSTERS
#6 GAMERA VS. MONSTER X
#7 GAMERA VS. ZIGRA
#8 GAMERA: SUPER MONSTER
The second GAMERA series:
#9 GAMERA: GUARDIAN OF THE UNIVERSE
#10 GAMERA: ATTACK OF LEGION
#11 GAMERA: REVENGE OF IRIS
The third series:
#12 GAMERA: THE BRAVE