In the Netherlands the thin fries McDonalds sells are referred to as French fries (franse frietjes): http://i.imgur.com/n0F248C.jpg.

Slightly thicker (square) fries are just called fries (patat): http://i.imgur.com/tui5FDe.jpg. These are served most often.

The big rectangular fries are referred to as Flemish fries (vlaamse frieten): http://i.imgur.com/QDwv9IA.jpg.