"Barring the original, what's your favorite version of Godzilla: the child-friendly superhero from the '70s, or the more anti-hero-like version from the '80s and '90s?"
Godzilla is somewhat like Batman to me in that I can enjoy both the more purely monster-like Godzilla of the 1950s-mid 1960s as well as the more anthropomorphic, kid-friendly, pro-wrestler persona of the late 1960s-1970s, just as I have no problem enjoying the Adam West Batman, the Michael Keaton Batman or the Christian Bale Batman.
Having said that, I don't find any of the Godzilla movies made between 1984 and 1995 particularly enjoyable. In fact I find them downright dull. The movies mainly consist of uninteresting human characters, plot elements stolen from high profile Hollywood movies such as Terminator 2 and Aliens, combined with scenes of giant monsters standing still and firing beams at each other until one of them falls over like a lead statue. All of this is watched on big tv screens by the military in a safe location so there isn't even any sense of danger from the allegedly rampaging monsters.
Things improve a great deal with Godzilla 2000 and Godzilla vs Megaguirus including a nicely redesigned Godzilla with massive pointy dorsal spines (as shown above) and some interesting adversaries.
My favorite version of Godzilla came with Godzilla, Mothra, King Ghidorah - Giant Monsters All-Out Attack (2001) which was meant to be the first of a series of one-off Godzilla movies that were sequels to the original Godzilla (1954) only, ignoring all of the movies that happened in between, and allowing for a variety of interpretations of the character and the series. In this movie, former Godzilla adversaries Mothra, king Ghidorah, and Baragon are all mystical, mythological guardian monsters who return to protect Japan from the attack of the evil Godzilla. And no mistake about it, this Godzilla is evil on a staggering scale. Redesigned with blank white eyeballs set in a fearsome face and a bulky powerful body, Godzilla is the unstoppable, brutal, embodiment of destruction (also of all the restless spirits of those killed in World War II) with powerful radioctive beams of energy which cause mushroom cloud explosions when they strike. What really makes this movie work, is that it doesn't flinch at showing the impact on human lives as Godzilla smashes the buildings they reside in, or blasts the soldiers trying to stop him. This is about as scary as a giant monster movie can get and is a powerful reworking of the original film including a journalist following Godzilla's wake of destruction as her soldier father tries to find a way to stop Godzilla. The humans are engaging, and their story feels like an integral part of the movie at large, but Godzilla is simply amazing.