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.