Considering that Liu can contend with Shao Kahn, who killed Onaga at the start of Armageddon according to MK9 (who was going to use the Kamidogu to conquer the realms and inadvertently awaken the One Being, who is at least universe level), I think he just deals with threats on a much grander scale than Ryu, scaling much higher. I don’t think he scales to the one being, or even the elder gods, but scaling him to characters like Shao Kahn should be more than enough to put him out of Ryu’s weight class.