Topping my list is the first-ever battle between the Marvel (Timely) heroes. It set a precedent which is still observed to this day, two ostensible superheroes duking it out in spectacular fashion. Namor was holding one of his many grudges against the surface world. Threatening to destroy an entire city, the Atlantean is confronted by the Human Torch, who is also a policeman. Their confrontation spills across two issues and would continue in later installments until the War briefly united the combatants in a common cause. It's two elemental forces of nature going toe to toe. What more could one ask for?