I am going to explain the Timeline, and I am bored 
 
  
1954- Godzilla is created from H-Bomb tests and destroys Tokyo, Godzilla is then killed by the oxygen destroyer 
 
1955-Another Godzilla appears and fights Anguiris, but destroys Osaka in the process, Godzilla is then frozen in ice 
 
1962- Godzilla then leaves from the ice and fights King Kong 
 
1964-Godzilla fights Mothra 
 
1964-Godzilla fights Ghidorah, with the help of Rodan and Mothra 
 
1965- Godzilla then fights Monster Zero (Ghidorah), and it turns out Monster Zero is being controlled by the X Aliens 
 
1966- Godzilla fights Ebirah, the sea monster 
 
1967- Godzilla's story about him and his son 
  
1969- A boy imagines himself being friends with Godzilla's son 
 
1971- Godzilla fights a monster created by pollution, his name is Hedorah  
 
1972- Godzilla fights Gigan and King Ghidorah  

1973- Godzilla fights Megalon, and Gigan I think 
 
1974-Godzilla fights Mecahgodzilla, an Evil version of Godzilla attacks Godzilla, Godzilla then defeats him with the help from King Ceasear 
 
1975- Godzilla fights Mechagodzilla and Titanasaurous 
 
1999- All though destroy all monsters was made in 1968, the movie takes place in 1999, basically all the monsters go crazy and attack the world, but in the end they beat the crap out of King Ghidorah 
 
well there you go, I got bored and did that, bye
 

Showa is the Easy one, during this Sagas, the timeline haved sense, the hard times are Heisei and Millenium.
Since those are Split Timelines, they almost make no sense.

"75-99 Godizlla was retired and lost his job and spent his years at home drinking pop and eating pizza infront of the t.v. until he made his big comeback in 99 is what I'm guessing? Ran out of monsters in those years. Hmmm... "

"Showa is the Easy one, during this Sagas, the timeline haved sense, the hard times are Heisei and Millenium. Since those are Split Timelines, they almost make no sense. "