Like the Hulk told the Abomination when Galaxy Master boosted him "You can be 10 times stronger than Hulk, and all Hulk has to do is get 10 times madder!"
Hulk knows his own power.
i don't agree that hulk has no upper limit i think in all the old handbooks it used to say he had apparently never shown his upper limit so it remained a mistery.I think the trouble is the hulk ultimately is a mortal and anything mortal by definition has a limit even rage,what you will find is hulk's strength can probably nowadays increase rapidly with his anger but ultimately the increase will almost start to level off over a longer period.
There is no doubt in the silver era he seemed to have a limit as the abomination literally killed him in their first fight and hulk only survived due to being healed by some kind of machine,even if his strength did increase with rage it seemed to take ages to notice any major significant increases(just look at any of his old fights with likes of abomination,namor,thor etc).
the bottom line is that in recent years marvel have definitely established the hulk as strongest mainstream hero without physical equal but that means nothing when comparing him ti likes of superman who is not in the marvel universe.It is like comparing apples and oranges i feel.