Doctor Doom first appeared in an issue of Fantastic Four dated July of 1962, which means that we now have fifty years of stories featuring Doctor Doom. He is primarily an antagonist of the Fantastic Four, but he also is a frequent opponent of The Avengers. He has been around often enough that it would be a difficult task to find a month in which he doesn't appear in at least one Marvel title. He has also appeared in a variety of other Marvel spin-offs, such as television, movies, and video games. In that time, some of Marvel's best creators, such as Stan Lee, Jack Kirby, Walt Simonson, John Byrne and Mark Waid, defined Doom's personality.
All of this is a prelude to saying that a complete history of Doctor Doom would be difficult to compile. And would be pedantic, since comic books are not heavy on consistency, continuity nerds to the contrary. And Doctor Doom has been many things in his history. Sometimes he is a slight variation on Lex Luthor, the jealous genius. Sometimes he is like Cao Cao, the amoral leader who believes he is entitled to break laws for what he sees as the Greater Good. Sometimes he is a theme villain, an evil Iron Man: just a thug in a powered suit. Sometimes he is working on an almost cosmic scale, scheming against Galactus or Mephisto. Sometimes he just gets punched out by Spider-Man. This is true of most comic book characters, heroic or villainous, but it might be more prominent in the case of Doctor Doom.
The basic portrayal of Doctor Doom will run along a continuum. On one hand, Doctor Doom is a cultured, intelligent man who loves the arts and always keeps his own code of honor, and is genuinely concerned about the people of Latveria. He is often dealing with events on such a cosmic scale that normal rules of morality seem not to apply. Doctor Doom is a bit of a Nietzchen uberman. On the other hand, Doctor Doom can also be portrayed as a vain, selfish, violent and petty man who uses his scientific genius as an excuse for being an immature narcissist. And then sometimes, the entire character spectrum is put aside and all Doctor Doom is, is a man in a suit who can blow stuff up. How Doctor Doom is portrayed is a function of the writer's taste, the current trends in comic book psychology, and what type of medium he appears in (television show Doctor Doom is going to be less sinister than graphic novel Doctor Doom). How the reader chooses to view him is a matter of the reader's taste, whether we read comic books for an explication on the nature of human evil, or whether we view them to see explosions and fisticuffs.