[Daikaijuman54]

I'd say start whichever you think looks best to you. But starting with the original, either the 1954 Japanese or the 1956 King of the Monsters, is a good start. The latter is a probably one of the best "Americanized" cuts, because the added character doesn't directly interfere with the story and acts more of an eyewitness we follow through the movie, the former for being the original, with some scenes cut from the latter, and also has a more somber feel.

Also, don't let general opinions drive you away from the ones many consider "bad," as it's mainly up to you whether you like it or not (I may consider doing a whole Godzilla Thread, where I talk about the movies, but I haven't decided). Heck, I've found enjoyment in the 1998, despite that I don't think it's bad nor really good, and even the Polygon Anime Trilogy has it's positives for me, it all comes down to what interests you (or anyone else looking to get into Godzilla).