Why you can't compare real humans to MU humans.
I know I have said before that you cannot compare real humans to MU, but there is also a bigger reason why you cannot compare real humans to MU humans, The Celestials. It seems to me that eventhough not all human beings have powers all human beings are mutants, in the sense that all human beings have mutated genes. I say this because.....
The Celestials made experiments upon the neanderthal men, resulting not only in humans- that's us- but in the cosmically-charged god-like Eternals, and bestial sub-human Deviants, who were cursed with an unstable genetic code, causing each new generation to be more horribly deformed than the last.
This was taken from http://www.geocities.com/brenni_au/XFactor.html
Interestingly enough there is this as well...
Moreover, on scanning the city of Anchorage for mutants in order to pinpoint Cyclops's location, the Master Mold discovered that human beings contain some mutated cells. Hence, the Master Mold decided that according to its programming to eliminate all mutants, all human beings must be destroyed.
The above was taken from http://www.marveldirectory.com/individuals/m/mastermold.htm
Therefore what is the cause of superhuman powers and mutation in the MU? The Celestials. This can explains why you have mutants and why humans can gain superhuman powers. It even explains how apparently normal human beings can do "superhuman" acts. In some cases humans need to mutate, but an ordinary human being can also gain superhuman powers by learning either martial arts or magic. Eventhough these humans do not have powers magic and martials arts if studied to an extreme level can give them the equivalent of super powers because they already have mutated genes.
In the real world this is what mutated genes do.
Research using recent molecular biology techniques is revealing that human cancers are caused by gene mutation. http://rerf.or.jp/eigo/radefx/late/mutatrbc.htm
Therefore the argument thats says a character cannot do such and such because he is human does not hold any weight because all MU humans are genetically different from MU humans, and this mutation is what gives real humans their potential.