Man you guys cover alot of stuff before I could get in on this.
First thing, Hulk/Spawn - After taking all things into consideration, nothing short of a soul stealing type ability, or just tottally disintigrating him is gonna get spawn to win that, unless he can get him to change back to Banner(Saw that in a what if). Maybe the Psonic attack thing but, I still say Hulk.
Next, Hulk/Thor(which I heard mentioned) - Am I the only owner of comics(not plural) were the Hulk hands Thor his ass(At least three comes to mind without much thought). As strong as Thor is, the Hulk has no cap on his strength.
Also, Gladiator/Superman(also brought up) - As powerful as superman is, there is a limit to his strength. Gladiators strength is dependent on his confidence. In otherwords, all he has to do is think he has the strength to win and he will. His run ins with the Xmen have all been ether stopped before it gets anywhere, or some telepathy thing going on, or him being blown far enough away that by the time he gets back there is no more fight. Gladiator would win, despite me being a superman fan.
And, Hulk/Superman(breifly mentioned) - Still Hulk wins. No matter how tough or strong you think Superman is, in a fight, the hulk will become as strong as it takes to put the pain on him. And lest we forget the hulk has a pretty hyper healing factor thingy(which superman cannot lay clam to).
As far as the order of strength thing in Marvel, would agree with you but you put Colosus in there, come one man, he is way down the ladder, way too many folks out there stronger than him.
Batman vs DareDevil would be really kool. Sounds kooler the more I think of it.
I think I hit everything, or almost. L8r guys it's been fun...