I find it interesting that most housecats are smaller than most domestic dogs, but that most domesticated dogs are smaller than the large-cat species. Of course there are some large dogs, but they’re hardly alpha predators.
It turns out that it is just how dogs have evolved. Whereas most cats are solitary hunters (which would favor size), most dogs are pack hunters (where size is mostly irrelevant). There are rumors of a very-old prehistoric animal that was the largest predator on earth, but both cats and dogs could very well come from it.
That said, the Malamute and the grey wolf (and, of course, the mastiff) are definitely close:
A Grey Wolf mix:
If there is any doubt that the Malamute is not an alpha predator: