<?php
query_posts( array( 'meta_key' => 'ratings_average', 'orderby' => 'meta_value_num', 'order' => 'DESC' ) );
if(have_posts()) : ?> <?php while(have_posts()) : the_post();
?>
<h2><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h2>
<?php the_excerpt(); ?>
<?php endwhile; endif; wp_reset_query(); ?>