Wuthering Heights is full of dualities in themes, settings, characters, and symbols. As the other editor has said, I would classify the symbols are "wild" vs. "civilized" rather than "good" vs. "evil":
- Man is civilized, the devil is wild. “Is Mr. Heathcliff a man? If so, is he mad? And if not, is he a devil?”
- Edgar's affection for Catherine is civilized, but Heathcliff's love for her is wild
- The ghost of Catherine in Part I is considered good, or at least harmless, while Heathcliff in Part II is considered evil: ("like the devil").
- The moors are considered wild, while the estates are considered civilized.
- The exposed Wuthering Heights high on the moors is considered "good" by Romantic sensibilities, while the sheltered calm of Thrushcross Grange is considered, be default, as "bad"
- There is much animal imagery that suggests wildness--which is usually bad: "rabid dog"
- Weather is usually wild: violent storms
- Doors and windows can be both: a closed door or window shows wildness, but an open one shows peace.
- Love is good, while revenge is evil.
- Death is considered wild, while life in the Linton house is considered civilized
I really don't think that Wuthering Heights is about the struggle between good and evil.
Although Heathcliff is pretty darn nasty, it's hard to see him as evil incarnate; he's more a case of a person overcome by obsessive love and jealousy.
Catherine (the elder) is certainly no saint with her two-timing of Heathcliff and Linton. Edgar Linton is a decent fellow, but a whiner, at least in his youth. Catherine (the daughter) is at times deliberately cruel to Hareton. Her cousin, Linton Heathcliff, is a pathetic crybaby who is an accomplice to Heathcliff's plot to kidnap Catherine and Nelly.
The only character whom I truly admire is Nelly. She is caring, loyal, and intelligent.
I suppose you can look at Wuthering Heights as a symbol of evil and Thrushcross Grange as a symbol of good. I, however, would prefer to see them as symbols of decay and civilization, respectively.