Boredom and dissatisfaction are great ways to start off a story. Seriously. Dissatisfaction often leads people to look for something to do, and that something often gets them into serious trouble. That's certainly what happens in Coraline. Coraline starts off feeling ignored and lonely. So when a weird hallway appears behind a mysterious door, Coraline take the opportunity to cause some trouble. She's curious and fascinated by the other world, but she also quickly realizes she wants to go home. After surviving a very scary adventure, Coraline seems cured of her dissatisfaction: it turns out excitement and adventure can be a bit over-rated.
The other ghost children weren't dissatisfied with their lives before being kidnapped.
Coraline's tendency to be a bit dissatisfied with things actually saved her in the other world, because she wasn't willing to just settle for whatever the other mother gave her.