Godzilla vs Gigan:
I actually watched this like two weeks ago but my brain has just not been co-operating when it comes to this stuff so some of these details will be 100% wrong.
Anyway surprise, aliens want to take over the Earth (in this case the aliens are giant cockroaches who fucked up their own planet with too much pollution). They've infiltrated society and are working on a plan to destroy Monster Island and thus pave the way for their own brand of "peace" which is apparently "everything but us is dead." They're doing this by building an amusement park themed around Godzilla, including a big tower shaped like Godzilla which also happens to house their DEATH RAY or whatever.
Our protagonist is a down-on-his-luck cartoonist who gets the chance to design some fake monsters for the amusement park. He runs into a woman looking for her missing brother, who has been press-ganged into helping build the death ray or whatever. They end up uncovering the alien plot, but the aliens summon Gigan to accelerate their plan. This also features Godzilla and Angurius talking to one another, and Godzilla sends Angurius to investigate at one point. It's all a blur. The message (pollution is bad we don't want to end up like the cockroach aliens) is pretty straightforward, and Gigan's design is... weird? He's like a beetle, but not really, and he has hooks for hands. Godzilla gets pretty fucked up in this movie, kind of like when he fought Hedorah, except instead of being covered in acid burns he just gets fuckin' cut. There's actual blood in this one, which kind of went away for a while, but now we're back to it and it feels deeply odd because these things have only gotten more cartoonish as they've gone along.
The fighting is pretty good, the tower blows up real good, and you get this incredibly dumb scene of two cockroaches buried under rubble talking to one another about how they can't believe their glorious plan went so wrong. It's... incredible.
3 out of 5 cockroaches.
Godzilla vs Megalon: Jet Jaguar's in this. Jet Jaguar is like Ultraman, except he's a robot and his ability to grow big is chalked up to him being just, really determined to protect people. That's not a joke, that's literally what they say and the movie just moves on like that's not a completely buck-fucking wild thing to say.
The protagonists are a professional racecar driver (I think?) and his inventor buddy (who built Jet Jaguar) and his... *deep sigh* precocious little brother. Yeah that's right we're back to this shit again.
The villains are the denizens of Sealand, an underwater kingdom that ends up being damaged by those goddamn americans (never mentioned that it is definitely the USA performing the tests, but it's definitely them) and their fucking underground nuclear tests. So the villains are at least justified in their desire to destroy all surface dwellers, because the surface dwellers started it.
Their plan is simple enough - summon Megalon and hijack Jet Jaguar's control systems to make him show Megalon the best places to destroy stuff. Why they know about Jet Jaguar is a bit of a mystery but honestly I don't want to put more effort into considering this mystery (also the mystery of why they need Jet Jaguar to show Megalon around, which.. huh?).
The inventor, of course, has a backup system they use to send Jet Jaguar to get Godzilla so he can whip Megalon's ass - but then the Sealandians or whatever they're called contact the aliens from the last movie and ask for help, so Gigan shows back up. Two on one isn't fair to Godzilla, so somehow Jet Jaguar gains sentience (I'll be honest I looked away for a minute and when I looked back they were like "oh he's making his own choices now") and then grows big because of his determination and there's a fight.
Jet Jaguar is a ridiculous looking robot, and he has a very dumb theme song. Therefore I am pleased to announce he has been adopted as my son.
The movie kind of sucks though.
3 Jets Jaguar out of 3