I believe that any dog has the potential to be a good dog if your willing to put the time and effort in to get him/her to a standard which you are happy with. But good breeding does help and can make the difference between a good dog and a excellent dog. As long as your happy with how your dog works and it gets the job done who can call you on it.
Most off these people who call everyone else's dogs useless but there own are full of s**t you can't have perfect dogs all the time.