The absolute best Peking Duck in the city is at Five Happiness Restaurant on Geary and 6th Ave. I was actually just there again this past Sunday. The duck is perfect and served with homemade pancakes. Plus, they make a soup out of the duck carcass.
The restaurant itself is very old and not all that clean. And I think most of their other food on the menu is only okay, but for the perfect Peking Duck, this is the place to go. We are actually thinking of ordering a duck to go for Thanksgiving then heating it up in our oven at home.
Most places do the Peking Duck on buns, rather than the thin crepe-like pancakes. I like Yank Sing because you can just get one or two orders, rather than having a whole or half duck. (Although they serve it with steamed buns, not pancakes.)
I understand that the "real deal" not only presents the wrapped item, but also takes the rest of the duck back to the kitchen afterwards and prepares it as a separate dish. I've not seen that, though, so it would be interesting if anywhere does that.