Original name in Japanese was Gojira which (I think) is pronounced roughly Gah-jeh-rah with no solid emphasis upon any syllabel.
Actually the first syllable is pronounced more like the word "go." The second syllable is usually pronounced somewhat like "jee" or "zhee" -- perhaps about halfway in between -- but in some cases it can sound more like "dzee." And the last syllable sounds about halfway between "ra" and "la." And I'm pretty sure the emphasis falls on the middle syllable as it does in English.
So
Gojira and
Godzilla are equally legitimate transliterations of a sound that's about halfway between them. In fact, in watching
Godzilla vs. Megaguirus yesterday with the Japanese soundtrack, I noticed the lead actress pronouncing it more like "Goh-dzee-ra" in some shots and more like "Goh-jee-ra" in others (keeping in mind that when I type "r" I'm referring to the Japanese sound that's midway between
r and
l). The main reason the American pronunciation differs is because of how we read the vowels in the word when it's spelled "Godzilla."
However, in 1993's
Godzilla vs. Mechagodzilla II, much of the movie is set at a UN-run Godzilla-fighting organization so there's a lot of English dialogue even in the original Japanese version -- and the English speakers pronounce it "Godzilla" exactly as we Americans do. And that film was produced by Tomoyuki Tanaka, the creator of the character, so it's as official as it gets.
Two Toho legends surround the origin of the name. One, that the beast was named after a very large man. Two, jira means whale in Japanese and Go a contraction for gorilla, ie, gorilla like whale. There are no definitive records to prove either.
Actually the name is a portmanteau of
kujira, "whale," and
gorira, the Japanese rendering of "gorilla." The legend is that the large Toho stagehand was nicknamed Gojira, i.e. "gorilla-whale," because of his size.
Also, in the film titles I've seen,
Gojira isn't rendered in kanji (Chinese characters), but in katakana, which are kind of like italics -- the syllabic symbols used for writing titles and foreign words, as opposed to hiragana, which are used for more normal purposes.
Gojira in katakana is ゴジラ.
...and even ignoring all pretense to theme, you can just do a dark, serious monster movie about a giant destructive lizard.
There have been some later Toho Godzilla movies that managed to be pretty serious and effective. I particularly liked the aforementioned
Mechagodzilla II. But they still pale next to the '54 original. The deeper meanings, the character focus, the emphasis on ethical and philosophical dilemmas over city-smashing spectacle -- it's more than just a monster movie or disaster movie. It's got a substance and importance that none of its sequels have managed to capture.