Raoul immediately fall in love with Christine when he saw her singing at the opera, f boy much? In my opinion, I felt like the relationship between Raoul and Christine happened a little bit too instant. Raoul obviously only fall for Christine after he saw and heard her sing, Raoul fall in love for her talents, and nothing else. Christine on the other hand, she loves Raoul back and later marries him because he is financially stable. Think about it, if Phantom never taught Christine how to sing and if Meg's mother never adopt her and brought her to the opera to train her into a talented actress, as a "childhood playmate" would Raoul ever fall in love with an orphan? This is also part of the main reason why Phantom becomes possessing and aggressive towards Christine against Raoul.
I'm more on Phantom's side since even though the things he does like teaching Christine how to sing throughout the years, and all that creepy things he does without showing recognition, at least Phantom truly loves Christine for who she is, he loves her when she was brought in as an orphan and he loves her throughout the her years at the opera. Sure, what Phantom did was creepy and messed up, but do mind this: he is completely detached from the society for his appearance, from interactions and from love. Knowing his own deformity, of course he would approach the person he loves differently than others, and I don't blame him. He might be aggressive and disrespectful, keep mind that he spent his childhood treated as a circus freak and his entire life hidden from the world with no interaction with anyone. Note that he at last DOES let Christine go with Raoul to let her be happy, but has Raoul ever done that?
He would never put Christine in harm's way unlike what Raoul did at the end when he used her as bait for the Phantom. Additionally he let her go. If he hadn't loved her then he could have kept her prisoner and only used her for her voice and sex. Instead he let her be happy. The most important piece of evidence for me was that he never forgot her.
Manipulative, creepy, overbearing, possessive, controlling, agressive, disrespectful...The perfect lover. Being dark and mysterious may be romantic, it doesn't make for a great relationship.
I think the main point is that she should end up with whoever she wants, hence her choice is always valid. Christine should be with whomever SHE loves and wants to be with, regardless of whether the phantom loves her or not.