It's a loving, hot-blooded recreation of storytelling for six-year-olds. Kick-arse music! Awesome animated action! Almost no content whatsoever if you believe that stories grow from characters!
To ignore the action scenes would be the ultimate sin in the eyes of this mini-series's creators. That's the whole point of the exercise. We're not supposed to ask what story purpose these scenes might be serving. There is no story purpose. Their job is to look cool. The episodes exist for the sake of their action scenes, with everything else (e.g. story, characters) being optional.
Ignoring the pointless stuff that sent me to semi-sleep, here's a synopsis. The following is the few minutes of watchable content amid a swamp of macho destruction that's impossible to care about unless you already knew and loved the characters before you started watching.
An utterly mad scientist called Dr Shikishima gets a cameo. He makes weapons for the heroes and he's the best thing about this mini-series, despite only getting about a minute's screen time in total.
A wrestler fights a blue-grey leaping weirdo with fangs. My first guess was "undead", but he's a dinosaur. The show's heroes watch the wrestler and cold-bloodedly discuss his low chances of survival. "We don't need normal people. If he dies, we're not interested in him."
The wrestler turns out to be a swaggering dick, so he fits right in. The evil dino mutant junkpile monster looks cool.
The government says "no" to the heroes because the adventure genre demands opposition, no matter how stupid. The mini-series never returns to this.
Jack and Mary King are the pilots of America's super robot, Texas Mack. They talk like a macho parody of Americans (with bad Japanese accents) and I wanted them to die.
Someone might have died, perhaps. It seems to have happened during an action scene, so I missed it.
Dinosaurs trash the heroes' base.
The latest baddie has a matter absorber that will ultimately transform Japan itself into energy to power his robot. Astonishingly, a fight now has some context beyond "FIGHT BADDIE". (Destroying New York or the heroes' base would sort of count, but that's more of a setting than something you need to pay attention to.)
Distressingly, the Americans are still alive. However the "mountain monkey" delayed insult made me laugh. (That hot-blooded wrestler isn't the brightest spark, so it takes him a few seconds to process.)
I actually like the cast. They don't matter in the slightest, mind you. Once they're piloting those robots, we're just watching lumps of metal thump each other. However they're rather endearing in how passionately over-the-top they are, even though Hayato has the personality of a stoic, manly paperclip. Also, Dr Shikishima is my hero. (His idea of celebration is to shoot hell out of the ceiling.)
It's based on an anime/manga franchise created by Go Nagai and Ken Ishikawa. Don't watch it, even if you're a Go Nagai fan... but do listen to the soundtrack. Getter Robo Go has some mighty songs.