I have to agree with the above to some degree. As much as I liked Beast Wars, toy wise (non Japanese) it had a monumental flaw and that was a lack of variety. They were all Beasts, about half were robotic with pseudo vehicle modes (Transmetals) but the Beast theme was still very much present.
Beast Machines tried to provide variety but making the good guys appallingly bad non robot toys and the bad guys drone like robots was not the way to go.
RID also offered variety but compared to BW, BM and Unicron trilogy it was not that prevalent in the eyes of the general public.
When Armada came out; on the surface it looked like they had gone back to their roots with cars, planes, etc and that is excellent and I know that originally this concept did catch my eye but when I saw the gimmick centric toys, cartoon and plot, it killed any enthusiasm I had for it.
However Armada was not the provider of variety as most toys were just gimmick boxes with a vehicle theme of some sort. It neglected variety.
Energon and Cybertron went for over the top Sci-Fi vehicle modes for their entire lines and again neglected variety. However as Dirge mentioned, the smaller toys did do an attempt at realism which worked amazingly well such as Clockers, Armorhide, etc.
The only line which was succesful at providing an excellent balance of variety between realistic, Sci-Fi, Beast Modes (organic looking and robotic) and gimmicks was G1. No line since has been able to provide enough variety to satisfy all tastes.