I love it when you get all deep and reflective Rach - it always makes for good reading!
Is parenting important? Yes, I think it is critically important. Is it determinative? Well no, as the examples you mention show, obviously not. I like what Amber said about providing the foundation, and its up to our children to build on that. I think deep down we all feel that parenting our children is possibly the most important thing we will do in this lifetime. Unfortunately that doesn't give us any guarantees about their future.
Still I think for most of the people who frequent this forum, we wouldn't be able to live with ourselves if we didn't give it everything we had.