Honestly, I don't think this is all that much better than raping an adult. At least a grown woman is more psychologically durable, and one can at least try to come up with rationalizations for it. But this is just amazingly abhorrent. I mean, it's his daughter. There's also tremendous harm to his wife involved. Count me with the "hanging's too good for him" crowd. Realistically, I'd want 15 years, though I don't really see the point of jail sentences for this sort of thing. It's not like we expect his attitudes to change while in prison, and he's surely done more harm to others than almost any amount of jail time could make up for. It's better than nothing, I guess.
I don't think the fact that she was his daughter can be emphasized enough. Just for dealing in child pornography, five years makes sense (and that may be what he was sentenced under). Maybe also for, without physical coercion, actually creating child pornography. But this was his daughter. He had much stronger duties towards her than towards a random child, much stronger duties towards his wife than towards a random mother, and what he's done is going to screw them both up much more than he could have screwed up some other random family by convincing their kid to take her clothes off for him.
