I don't like the idea that one specific choice in life can make you a success or a failure. Certainly not one that doesn't affect anyone's life but your own.
People have only had the choice to not have children for around 50 years now. Before that, being childless carried a huge stigma because it meant that you were not able to reproduce. Being "barren" was shameful (and usually blamed on the woman - go figure). All throughout history, if you had sex, you were going to have children. Fact. Not having children meant that in the eyes of society, something was seriously wrong with you, because you either weren't able to have children, or you weren't having sex with your spouse.
I don't think I want children, but I'm not sure. I am young and depending on my circumstances and whether I end up with someone who wants kids, I might change my mind. But I really don't think it's a problem that some people are more discerning about when and if they have children. It's much more common for people to have more children than they want or can afford. The only way I would have a child is if I truly wanted one and knew I could give it all the love, care, and financial security that children deserve. That said, I think I'd be a horrible mother and my genes aren't so great either. I think there are some people out there who would be better off NOT passing their genes forward. If I don't, the human race will move forward without me. One person's genetic contribution is like dumping a thimble full of water into the Pacific Ocean. That's about the amount of difference you've made, for good or ill.