I found it rather... mediocre. I enjoyed the human drama interlaced into the first Godzilla movie. It felt very much like the original 1954 version to me, with strong atomic parallels. The second, much to the enthusiasm of the fans, featured much more monster action. It seemed very "Heisei Era" to me. Monster action, strong morals, strong human characterizations, no goofy, silly schlock.
GVK feels like it's a move set dead center in the peak of Showa Era Godzilla. Showa Era Godzilla was marked by characterizing Godzilla as this kid-friendly, silly, almost superhero type figure. He became a single father, formed a Kaiju Justice League, it was all very schlocky. GVK is no exception. A child is able to teach Kong sign language... secretly, Godzilla acts almost human in movements and mannerisms, and it's all tied together with rather lower quality visual effects. At least, low quality by today's standards.
This contrast is even starker by the fact that the previous two Godzilla films kept the effects very grounded. It wasn't bumbling like a man in a rubber suit, but it felt realistic. That all goes out the window with GVK. The movements are fast to the point of ridiculousness for creatures of this size, and I almost half-expected Godzilla to do that tail slide thing from Godzilla vs. Megalon. In all, I was actually kind of disappointed with this movie. It seemed like it had the potential to do something great, but took the schlock route instead.