Quick pic I took this morning from my local store where at least 5/6 various references of ketchup can usually be found (sometimes more, premium quality mainly).
Traditionnaly, we don't dip fries into sauces. I would say that good fries don't need any sauce. Salt and maybe pepper should be enough.
On the other hand, Belgian fries are thicker and are made to be eaten with sauces.
WTF, french and belgian fries? Yep, two different recipies
