(if you've read this far in the thread, you're probably spoiled to this level anyway)
I personally liked Kotori's route precisely because of the feeling of powerlessness, futility and general depression it invokes. I assumed kotarou ended up with the girl at the end due to bishoujo-ge logic, so that was not a problem to me.
Also, I personally disagree that Terra is depressing, but maybe that's just me.