I wasn't going to reply because this topic has come up before, but I can't help myself!
When you're looking at dogs as being related to wolves, you can't just look at reproduction as a deciding factor. It's one trait out of billions that are related to genetics. They've done studies of the dog genome to determine relationship to wolves and have found that, despite existing for longer as a whole, most ancient breeds are actually closer related to wolves. It makes sense if you think about how the dog's were produced. Ancient breeds developed somewhat naturally where dogs created more recently have had a lot more human intervention. It stands to reason that this human selection would create dogs that are genetically further from their ancestors.
As far percentages go, it's already been explained really well, but since genetics are random, you might get a "20% wolfdog" and "80% wolfdog" out of a litter produced of a pure wolf and a dog. When it comes to breeding, then, if you think about the traits you breed towards are the more dog-like ones, you more quickly breed away from the wolf genetics despite the number of generations.
Here's a page that explains it well, and shows actual examples:
http://wolfpark.org/ccpage3.shtml