I agree that this is a very illogical movie. In fact, I concur with jelly on most of the complaints (Why was the chopper destroyed and why was it forgotten? Why do the Futurians need to bring anyone back in time? etc.), though I do enjoy the kitschy effects associated with the Futurians. Would I call this a poorly scripted film? Yes, definitely. That said, I still think Omori has written (mostly) believable and likable characters here, especially Terasawa and Shindo. Emmy is a good character too, though her motives are very foggy. Why did she deposit the Dorats on the island if she knew they'd turn into Ghidorah?*
The thing is, I just love the movie. As I said, the script is basically falling to pieces for the duration of the movie, but it's just so fun!
I'm sure I've posted in this thread before and I know I have elsewhere, so I won't go in depth, but (to me), there's just so much to like here. You've got an incredible portrayal of Godzilla and a cool update of King Ghidorah, even though he's got nothing on Tsuburaya's original. You have androids, time travel, laser beam battles, cheesy English dialogue stolen from better films ("Make my day!"), WWII, Godzilla as a dinosaur, above-average Kawakita miniatures,
Mecha King Ghidorah, and Yoshio Tsuchiya and some gaijin getting blown away by Godzilla. Speaking of the gaijin, I think the ones in the main roles here are pretty good for being amateurs. The poor WWII-era actors are awful, though.
TL;DNR: Yeah, I know it's a bad movie, but so is GODZILLA VS. GIGAN and I cherish that too.
*I think the answer to this is actually that Emmy knew and was only going along with the plan to blackmail Japan. Doesn't she say that at one point? Maybe not in the dub, anyway. She just takes offense to Wilson and Glenchiko's use of the monster. She doesn't want to destroy Japan, just frighten them. That's how I understand it, though it's very clear at all. It would probably just have been better if Wilson had gone along instead.