James's real reason...

[shootzombies]

We know from Silent Hill 4 that the Leave ending isn't the right one at least.

Some people assume that, but it's incorrect. Silent Hill 4 doesn't invalidate any of the endings in Silent Hill 2.

Frank Sunderland never sees his kid again, we hear nothing of the mother so it would seem Frank is it for James' family. If he didn't contact his dad, chances are he never made it back to the land of the living.

Since the SH series are games and there are gaps of information, no one can be absolutely right about anything, there is always room for doubt. A little intelligence and reasoning though can lead to sound observations and theories. All of which are open to mature discussion.

Well considering what you said about James not contacting his father, it would seem that only the "In Water" ending and perhaps the "Rebirth" ending are the only true endings to SH2.