An American icon is marking his 40th anniversary. On Nov. 21, 1976, movie audiences met South Philly boxer Rocky Balboa. Four decades later, the lovable loser turned heavyweight champion still resonates with fans. His underdog story against the gritty backdrop of a blue-collar city is one of the most celebrated in American film. ''Rocky'' was made on a budget of only $1 million, but it went on to make more than $225 million worldwide. The film also won three Oscars, including best picture, and made a megastar out of Sylvester Stallone, who wrote it.