human factor in kamem rider

[Kamen Rider G]

I notice that the human factor in kamen rider has change a lot since it first started, at first it was monsters wanting to take over mankind but now you have human being taking over by some force of there own free will, make you think really how we go from evil monsters wanting to kill us to us trying hurt each other  

[Katsumi Daido]

Den-o fights monsters from the future, it is their own choice to an extent. I'd consider Den-o the first series that took that concept.
I'm going to say that W is most likely the best example for your point.
OOO, I'm on the fence about this one, some of them are (kazari's yummy) and, then there are a lot that aren't, but they all are based on the human's desires.
Fourze would definitely be another one that fits.

It's an interesting thought, I rather like the idea since it's not some external force, it's our own desires manifested by an external force.