Ayn Rand once noted that the modern heirs of the Romantic tradition in literature - that is, genre fiction such as spy thrillers and mysteries - tended to have problematic heroes. Such things could not happen to such people, she said, meaning that the exciting adventures of the plot were impossible to reconcile with the bland Everyman characters.
This is not a problem with her writing. Rather, Atlas Shrugged is overloaded with heroic heroes and evil villains. Perhaps because her notions of both good and evil are unusual, the characters tend to blend into one another, feeling the same joys or fears (the good feel joy and the evil fear), having the same reactions to the same events, and so on.
The Fountainhead has a great advantage over Atlas Shrugged in this regard, because that shorter novel has room for only one of each Randian type - the Hero, the woman who will eventually see the heroic light, the man who should have been a hero but went wrong, the penny-ante bad man, and the truly evil man. It’s also an earlier work, from when Ayn Rand saw more of a possibility of human variation; in Atlas Shrugged everyone starts out farther along the road to good or evil, and the entire world is forced to make a choice in the end.
The problem of good and evil characters comes up even if you’re not writing your own personal apocalypse. Ayn Rand thought most Christian fiction (by which she meant Hugo and Tolstoy, not Lewis and L’Engle) failed on both counts - that the Christian ideal had proven impossible to project into a fictional hero, and that the corresponding villains frequently ended up as strangely sympathetic characters. She based her own characters on a different division of good and evil.
Her evil characters in The Fountainhead are quite successful, in that it’s only the , dying flashes of goodness within them with which the reader sympathizes; they are otherwise despicable yet still believable. There isn’t much good left in the bad guys of Atlas Shrugged, yet they, too, avoid the twin bad-guy perils of being unbelievably, even comically, vile, or on the other hand, being attractive or sympathetic characters.
Roark is an engaging hero in The Fountainhead because he simply is the way he is, out there in the open for all readers to observe. The heroes of Atlas Shrugged are all so busy off-screen saving the world from altruism that it’s the people stuck in the middle, Dagny and Rearden, who become the protagonists by default. It’s telling that the real hero goes unrecognized for two-thirds of the novel, though it’s done very cleverly.
The great danger of good guys is that their very goodness will make them blander than their moral inferiors - not the bad guys in this particular case, but the characters who haven’t yet seen the egoist light. When there’s no one of interest caught in the moral middle, the bad guys can outshine the good guys. This has been going on from Lucifer’s speech in Paradise Lost to Khan’s (recycled from Melville) in the twenty-third century.
It’s not clear whether the writer has to change the definitions of good and evil in order to avoid the problem, but that approach worked for Ayn Rand.