G2 had a much more creative take on its Islands locations, G1 had us travel across its Island.
G2 had the most detailed masks to date (MoCr, MoCo), G1 had a lot more mask variants.
G2 had a much more mechanically and visually interesting combiner feature, G1 had technic vehicles.
G2 had a lot of coloured transparent pieces for many different parts of the body, G1 had a lot of coloured pieces for many of its different parts of the body.
G2 had a Gold and Silver fetish, G1 had Silver and Grey fetish.