Books of Doom and FF #247 are two stories I would point anyone to go read to understand what Doom is all about. And it's not that hard to know what he wants: power. The power to exert his will to overcome all things. First, it was to trump Reed Richards, who was the only person to ever prove him wrong, and more recently, the power to bring his mother back from the depths of Hell.
He is on one hand a dictator, but on the other, the people he rules over all love him without mass indoctrination. There was a line from the Superman cartoon in an episode where he defeats Darkseid on his homeworld, and as Superman is about to land the killing blow, his subjects run to protect Darkseid. When they carry him away, Darkseid says to Superman, "I may be many things, Kal-El, but here... I am God." That's never left me and I think that perfectly sums up Dr. Doom. Not just his relation to his people but how he sees himself, as well.