I'd have to go with Narmoto for G2; even though some aspects of the figure are simplistic, and there is a serious lack of elbows, the chest design is still pretty unique and seamless looking, and the color svheme is pretty well distributed. On top of all that, the shoulder-mounted gatling gun was a great idea.
As far as G1 goes; it's any of the Toa Metru. Not because they're actually good. Only nostalgia at work here.