Seriously, I doubt Stan Lee sat down and thought of Hulk as the MOST POWERFUL THING IN DA MARVEL UNIVERSE, rather than an actual amalgam of Hyde/Frankenstein archetypes. I mean really, conceiving of a character for the sole sake of his power level is like building a nuclear weapon as a "deterrent for war".
Of course, Superman was conceived on the basis of his power-level, but only in terms of how he relates contextually with the common un-Supermen of his Metropolis, in that he really is meant to be more of an Ubermensch than anything else. (Damn, just when I swore I wouldn't insert a foreign-language word this week).
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HULK EATS BRAIN OF PUNY POSTING GUY! HULK IS STRONGEST THERE IS!! Um, amd HULK STRAIGHT!!!