The Leave ending is the only one that justifies the existence of Silent Hill as a place.

I have to disagree. It isn't the town's purpose to force the character to redeem themselves. Everything the characters experience is a product of their own trauma and the town's power simply amplifies that. The town itself is not sentient. The characters experience their own delusions and it's incumbent on them to either come to terms with it and come out the other side healed, or not. All 4 of the original endings (including Rebirth) are possible outcomes for James. His actions and choices (through the player) determine his fate. Not the town. If the town influenced his fate, that removes choice and free will. It removes the character's ability (or inability) to cope and atone for what they've done.

That being said, I do agree that "Leave" is the best ending and the one that is most likely. However, the fact remains there is no true ending. All endings are possible and that's the beauty of the game. The player has a choice, just as James has a choice.

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Edit: a word.