TBH I've only really seen the 'Headmasters' series; I've not seen Scramble City, nor any of the other Japanese series... YET.
I quite liked the Headmasters series for its treatment of characters & its overall quirkiness that I'm sure is purely due to something being lost in translation.

The Japanese portion of G1 has most definitely served to offer some extremely cool, unique & distinctive characters (Hence figures) over its duration as the Japanese really seemed to use this period to experiment with all sorts of concepts & ideas.

I think this era still holds a degree of mystery about it, but the fact that certain facets from throughout Japanese G1 seems to constantly creep into the Western side of things must surely reflect that it has done enough to reflect its importance to the overall scheme of the brand & franchise.