Each post is showing twice in my custom query…?

There is really no reason to use raw sql to query posts. You can accomplish just about any type of query using the WordPress API. For full reference see the codex, Function Reference query posts. Try the following:

global $post;

    $args=array(
    'post_type' => 'tutorial',
    'orderby' => 'comment_count',
    'posts_per_page' => 10
    );

   $posts= query_posts($args);

foreach ($posts as $post) :

//do stuff

endofforeach;