Superman vs. Batman requires PIS, because Superman is the Hulk plus laser beam eyes, x-ray vision, freeze breath, flight, superhuman senses, superhuman reflexes, super speed, and super intelligence, and Batman is Wolverine minus the fictional uber-metal skeleton/claws, superhuman speed, superhuman strength, superhuman reflexes, and regenerative ability that'd allow him to resist a blow from someone with Superman/Hulk-level strength.
And we're not expected to buy that Hulk vs. Wolverine is a fight worthy of being made into a major motion picture.