Wordpress Popular Post Sorted by Comment Count

template.php

<?php
/* Add this where you want to display popular post sorted by comment count */
$args = array( 'orderby' => 'comment_count', 'numberposts' => $rtp_post_count, 'post_status' => 'publish'  );
$posts = get_posts($args); ?>
<!-- Output Markup -->    
<ul class="rtp-most-popular-wrapper"><?php
   $count=1;
   for($i=0; $i<sizeof($posts); $i++){?>
     <li>
       <a href="<?php echo get_permalink($posts[$i]->ID); ?>" title="<?php echo $posts[$i]->post_title; ?>" target="_blank"><?php echo $count.'.  '.$posts[$i]->post_title; ?></a>
     </li><?php
     $count++;
   }?>
</ul>