There IS no top level for Hulk since his strength is tied to his anger/rage. The madder he gets the stronger he gets so there's no way to say where his power level stops. Now, I'd agree with you that Big G would stop Hulk on any given Sunday in a regular book, but throw them into a MAX book and have Big G cut off Betty's head in front of Hulk and I bet Hulk could take him. Also, there was an issue of Fantastic Four where the Invisible Woman took out Galactus by herself by stabbing him with a really big invisible spear. I think it was her "Malice" persona or just after. As far as the FF are concerned Sue is the most powerful hands down.
if that happened...bad writing, !
hulk could be as made as crazy, no way he could stand a chance against a pure force of universe...that's just even beyond our parameters of "sheer srenght"...big G and T are on another scale/level.
regards