Strictly speaking, given the ubiquity of businesses such as McDonalds, Burger King and KFC, in British English, we now have both expressions. French fries are American style cartofi prăjiți - they are thinly cut. Chips are British style cartofi prăjiți and are generally much thicker cut, crispy on the outside and fluffy on the inside. We also tend to put salt and malt vinegar on them, which pretty much makes us unique I believe! It gets really confusing since most of the rest of the world seem to call thin slices of fried potato chips whereas we call them crisps.
Agree with all comments so far. "Chips" is standard English. "French fries" has been imported from America. Nowadays both should be accepted, though French fires are smaller than chips.