Ability to increase his strength to almost unlimited while increasing his anger levels.
Hulk is capable of jumps that allow you to cover several thousand miles away in a short time (it can get out of the orbit of the planet, which is considerably larger if we escape velocity to be reached).
He can hit your hands on a slap that creates a shockwave able to extinguish a huge forest fire, destroying structures or break all the windows of a city equivalent to New York. The power of this attack can outdo any hurricane ever to hit the Earth in its millions of years.
His Beats are so powerful that they have been able to perform amazing feats such as destroying an asteroid twice the size of the earth, light and heat to create an entire cosmos or destroy an entire dimension with just applause.
Hulk has incredible resistance to physical damage. It can withstand the impact of an artillery cannon caliber anti - tank bombs or explosions of gamma (higher than hydrogen) without appreciable damage weapons. It also has a high resistance to extreme temperatures and can withstand -150°C to 6000°C without abrasion or irritation (but you can get to resist attack nova Human Torch is 1 000 000ºC without appreciable harm witness Hell fire and produced by the Ghost Rider which no heat, fire or whatever the mortal universe can overcome).
Resisted the powers of Charles Xavier, Jean Grey and Cable (all omega level mutants), and even freed from the possession of the god Loki by his uncontrollable rage.
Hulk has accelerated tissue regeneration and can heal parts of your lost or damaged body almost immediately (the fastest Marvel Universe regenerative factor, even faster than the Wolverine himself) in seconds.
Superman can fly very fast and run as fast as Kid flash,
X-ray vision, telescopic and temperature,
super-tuned one ear, his mind is like a computer,
can speak all the languages on earth and even from other planets,
is invulnerable bullets.
The power of flight is the best known of all abilities of Superman, when he goes to take flight almost always grab a tiny boost and once taken up, can fly at will and maneuvered among the skyscrapers of Metropolis.
Although it is against his principles, he can rewind time, his molecules are vibrating and rotating around the earth at high speed, can create an energy field that makes what is closest to his body (such as his super suit) is invulnerable.
With all his superhuman powers can be hurt, bleed and can die.
I think Hulk would win because his is almost invulnerable, his healing factor is the fastest there is, he has more strength and Superman is almost invulnerable to everything but who know is he'll resist the Hulk (plus, Hulk can destroy an entire dimension).
Leave your opinion on who would win and why. Who would you like to have in the next hero battle?