I'll start with this: I love the movies, but the writers absolutely ruined Ginny's character and did the couple no justice. No wonder so many people think Harry should've been with Hermione - Ginny had no personality and Ron was an enormous jerk! If they read the books a little more thoroughly, they would see the four points I'm about to make (and many more besides).
1. They grew as people before they were together.
GiphyA strange reason to think two people should be together but hear me out. While Ginny starts out with an all-consuming celebrity crush on Harry Potter, The Boy Who Lived, she slowly becomes a strong character that is completely independent of Harry, despite the only times we see her being from his point of view.
Throughout the books, we learn that Ginny is a fierce girl who has a wicked Bat-Bogey Hex and a talent for Quidditch that rivals Harry's own. She stands up for her friends and fights for what she believes, completely decimating the typical "popular girl" stereotype that could have easily embodied her. She becomes more than just Ron's little sister with interaction she and Harry have. On the other side, Harry too becomes more than just "the hero who conquered the Dark Lord."
In a similar vein, Harry learns to love with all of his heart and fight for his friends, leading his classmates to see past the lightning bolt scar. The more he learns about his magical background and his parents, the easier he sheds the skin of insecurity the Dursleys gave him.
2. They were friends before they were a couple.
GiphyOkay, so this isn't always necessary to have a great relationship - my own is proof, but that's for another day. However, for Harry and Ginny, this built a foundation that would have otherwise been lost. Becoming friends is the best way for Harry to stop seeing her as just Ron's sister, and for Ginny to see the boy underneath the fame.
They develop a unique rapport that comes naturally as they grow older and more confident in themselves, and oftentimes it was Ginny who reminded Harry of the most important things.
"Anything's possible if you've got enough nerve," she says. And she is always right.
3. They create balance together.
GiphyWhen Harry gets stuck in his own head, it's Ginny who yanks him out of it with a well-timed reminder of her own experience being possessed by Voldemort. "Lucky you," she tells him when he admits he forgot. While Ron gives as much brotherly support as he can and Hermione brings logic to his troubles, Ginny uses blunt honesty. She is not afraid to call Harry out. This is true even in their breakup at Dumbledore's funeral; "It's for some stupid noble reason isn't it?" She knows what he plans to do, and even if she doesn't agree, she lets him make the choice - but not without making sure he knows exactly how she feels about it. And then, while he's gone, she strikes back against the Death Eaters in Hogwarts and does everything she can to keep the students safe, wreaking havoc along the way.
Harry fights out in the wizarding world, and Ginny fights in the school that they grew up in.
4. They share a similar kind of trauma.
GiphyAnd the trauma isn't just similar - it's caused by the same person. Voldemort took Harry's family away from him before he could even form memories of them, leaving him in a household that didn't love him. He possessed Ginny when she was just eleven, the first time she had ever been away from home, and stripped away any innocence she had about the world very quickly.
Ginny more than anyone can understand Harry's fears about Voldemort being in his head because she lived through it herself. The rest of the wizarding world, even Harry's closest friends, can only imagine what that is like, having Voldemort interwoven into their very soul.