Zelda wasn't any different in any other game. As far as I can remember, she was always pure, selfless, and put her people before her own self. Dark Link is an enemy, that may or may not have been created by Ganondorf. I actually don't think Dark Link is the opposite of Link, or his inner evils. Like Zelda, I also do not think that Link really has any evils. I know that sounds crazy; Everyone has some kind of evil inside. But Link isn't exactly human. He never talks in the games, we never know how he feels. We don't know if he wants power. Because we control him, we don't know what lengths Link would go through to save someone, whereas we know what Zelda would do.
Basically, I think Zelda is too pure to have a Dark side. I also think Link is too inhuman for Dark Link, the enemy, to really mirror his inner evils, if any really exist inside of him.
However, Ganondorf is a completely different thing. In WW, we saw that he attempted to use the Triforce because to save his people, the Gerudos, from the "evil winds." In OoT, he was just power hungry. So we see two sides of Ganondorf. One side that has good intentions, but just went about them wrong. The other side that just wants power, needs power. Which is the real Ganondorf? The conflicted, yet human, baddie? Or the power hungry demon?