In that situation, when Mario moves, you trigger his "hit" method if he moves into a Goomba (and probably trigger the Goomba's "bounce" method). If Mario is standing still and the Goomba moves into him, the Goomba triggers Mario's "hit" method, and its own "bounce" method. No matter the situation, the two colliding bodies are going to affect each other. It's the moving one that initiates the collision event, no matter how you code it.
Otherwise, what you're suggesting would require that every body be continually scanning for collisions, even when not moving, which would be much less efficient. I'm not really sure how else to describe it, other than to suggest you experiment, look at examples, and see for yourself.