I used to review fast food joints on a blog, and even tried some with friends when I still had some IRL friends. One important criteria for the fries was whether we liked eating them plain, with nothing else. If we need any condiment, then either the fries are too bland or unpleasant, and I know from experience that fries can definitely be very tasty on their own. But if I do use something with the fries, it will be barbecue sauce, or curry sauce (not just curry powder), or salt. Vinegar is also okay for fries prepared the Belgian way, with two baths with oils at slightly different temperatures, making them quite soggy.