Morgoth wasn't a human! He was one of the Ainur who could change form to fool the foolish humans! Older than the elves, having lived forever, he was able to pull off many fantastic feats of magic, including creating the orcs from elven prisoners! Gandalf and all the five wizards weren't human either, rather of the Istari sent from Valar who took the form of men, but where not men themselves. Sauron was one of the Maiar, not a human at all, but like the Melkor/Morgoth he could change shape at will.
Human wizard are vain, megalomeniachal, yes... but powerful? I don't think so