Most films are based on the idea that for drama you must place obstacles in the way of the protagonists' goals. Specifically for romances, the obstacle is placed in the way of the two lovers coming together. In romantic comedies, the obstacles are overcome, in tragedies, they are not. Romeo and Juliet face an obstacle familiar to most of us, the prejudice that exists between different ethnic/class groups. This is demonstrated to great effect in Bernstein's update, 'West Side Story'.