I am going to have to go with Sonic. The logic is simple, we have much, documented proof of Sonic helping animals out (see: Sonic 1,2,3 etc). When they had been encapsulated in some way by robotics, he freed them, and asked for no thanks in return.
Mario on the other hand stomps on any living thing that crosses his path, be it turtles, dragons, fungi, or bullets. Sure his Princess saving skills are unsurpassed, but is he an animal lover? I think not.
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