I definitely think genetics have a lot to do with it. I am 38 this year, have forever eaten loads of fruit, drank cordial and copious amounts of soft drink and I don't have any fillings. I had a wisdom tooth removed recently as it had broken from when I accidentally bit down hard on the ball on my tongue piercing a few years before and it slowly broke away.

My eldest son had terrible teeth when he was younger, to the point that I flossed and brushed his teeth for him. Once his permanent teeth came through, his teeth have been fine.