It's exactly like kids - there has always been the debate about will nature or nurture have the greater deciding factor in how a person or animal will turn out. To be a truly great dog i think it takes both.
That doesn't mean that you need famous lines or names, just a dam and sire( and preferably further back) that have proven that they can do their job and that they are free of health defects. These kind of pups seem to have it from a young age, at 8 weeks they are already alert, watching, ready to chase, and exhibit all the makings of a great dog even before you do a thing.
Howe