There are thousands of Protestant churches, so the answer depends on which Protestant church you're referring to. From my perspective as a Catholic, I'd say about 90% of the protestant churches out there accept basic Christian doctrine that has existed over the centuries so they're legit Christians. Pretty much all the Baptist, Lutheran, Methodist, Presybertarian, etc. churches would fit this catergory. On the other hand, Unitarians would probably fit the "Protestant" label, and that church won't even say for sure if Christ is divine. Are they true "Christians"? I think not.
I don’t consider Unitarians as Christian or Protestant.