I would have to say "it depends". I have owned Ford, GM, Toyota, Nissan, Volkswagen, and Mercedes cars--more GM than any of the rest (though you could not give me one these days).
I have used Lee, Purolator, Deutsch, FRAM, WIX, Baldwin, Motorcraft, A/C Delco, Mann, Mahle, Mercedes, and Hengst filters.
I have used Quaker State, Amalie, Havoline, Conoco, Motorcraft, Kendall, Castrol, Mobil, Gulf, Valvoline, Citgo, Chevron, Amsoil, Shell, and Pennzoil motor and gear oils.
Do I have preferred cars, filters, and oil? Yes, but not to the point of stating that I am brand loyalist.