@SpeedForceSpider: But, with what? I understand very clearly that neither is stomping the other, but what does Arceus have that Mewtwo should worry? As Mewtwo is faster, it is able to use Amnesia to boost it's own special offensively, and due to being RBY Mewtwo, resistance to incoming special attacks also. Something else from the same site is right here:
There are a few differences when it comes to a type's effectiveness against another type in RBY.
- Ice attacks are neutral to Fire instead of not very effective.
- Poison attacks are super effective against Bug instead of neutral.
- Bug attacks are super effective against Poison instead of not very effective.
- Ghost attacks will NOT work on Psychics instead of being super effective regardless of what any RBY type chart tells you
So, ghost Arceus won't work, Dark and Steel Arceus don't exist for RBY Mewtwo (this is because RBY Mewtwo doesn't have a weakness to Dark in it's programming, as well as his attacks not being programmed to be not-very-effective on Steel.) So, pretty much all Arceus got for Super Effective is Bug-Type Judgement. And then, like I said, there's the aforementioned Amnesia that can weaken the damage it does while also boosting what Mewtwo can do in return.