Like, I already knew that Toho had taken a shot at making a character in imitation of Ultraman, Zone Fighter, who is notable for 1) being much more brutal than most of the Ultras (I have an old blog post where I comment on this, but the embedded video is long gone and a bit critical to my commentary-but most of it had to do with decapitations, dismemberment, and/or extended application of rapid-fire projectile weaponry, so you can sort of guess at it), and 2) having Godzilla and King Ghidorah guest star here and there.
But I'd never heard of Assault! H
These shows are even more obscure than Zone Fighter, and, for that matter, much more obscure than Zone Fighter, because while I've known at least a little about Zone Fighter for a decade or so, I first heard of these three while wikiwalking last week, and I'd rather thought I'd heard of most of the "kyodai (giant) heroes."
There's not much to be found on YouTube for the obligatory embed; two of the series have exactly nothing. Go! Greenman does have an intro sequence available, at least, so there's that.
And while I can sort of see why the Godzilla wiki presented the statement that Godman resembles Ultraman more (presumably because of his color scheme), I look at Greenman and see Ultraman wearing a costume to avoid a lawsuit.
From what I've read, it's also amusing to note that Go! Greenman was a show featuring an Ultra-like warrior fighting super sentai/Power Rangers-style villains, with mooks and growing monsters of the week. Japan doesn't mix and match its different henshin hero subgenres enough.
*Assault! Human had the interesting quirk of its Ultra-like protagonists being called "humans" in English. Who knows what's up with that.