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In defense of the MegaroGoji, the face went through some pretty big changes to eventually look fierce. I'm no fan of the friendly looking 1973 iteration, but by the time 1975 rolled around he was a much angrier looking beast. The brow was lowered, making him look permanently infuriated, a ridge was added on top of his head and his muzzle was reduced so that he looked like a rugged action hero--The lip curl and angry brow gave Godzilla a Clint Eastwood/Sly Stallone-esque scowl. He looked like a god-like avenger.

I don't think the 1975 iteration, sometimes dubbed the MekaGyakushuGoji, should necessarily be lumped in the same category as the 1973 MegaroGoji. The minor updates make a huge difference--Even the 1974 updates (MekaGoji) made him look more serious. Long story short, he was friendly in 1973, but in 1975 he was a disgruntled, seasoned action hero:

 Anywho, clearly, and specifically, 1975 is my favorite suit. MekaGyakushuGoji all the way.

Eh best is a hard one. I want to say Biogoji since it's my favorite, but Ghidogoji is probably the "better" suit. I'll give it to Ghidogoji just slightly.

Worst:Musukogoji

Favorites are 1989, 1968, 1962 and 2000, I've always liked the latter two for their vaguely crocodile facial structure, while the former two for  being sort of the best overall entries for making G look powerful and aggressive.  G14 gets an honorable mention though, it's not a perfect design on the whole but where it gets it right it really gets it right.

My favorites are Legendary, Shin, 2000, GMK, Heisei (includes Burning), Kiryu, KingGoji, ShodaiGoji, 1998 (Yes, I admit it), Final and Mosu. 

My absolute favorite is either GMK or 2014. It's really close.