In 2007 Sight & Sound began compiling review/best of the year-lists which with the exception of the year 2008 have been published annually in the magazine's January issues ever since. In addition to selections by S&S staff, the lists feature films chosen by international critics. Each critic picks films (usually five) they consider their favourites, the best or most culturally significant of the year. If they wish, they may pick older works, provided that the films have been re-released on video or in cinemas during the current year—that's why a few pre-2006 movies pop up from time to time.
The list you're looking at right now is a fusion of the lists published in the printed edition of the magazine.