Create a list of recent Custom Post Types posts

You can use custom variables ($recentPosts) like this:

$recentPosts = new WP_Query(array('showposts' => 9, 'post_type' => array('mycustomposttype1',  'mycustomposttype2','mycustomposttype3')));
while( $recentPosts->have_posts() ) : 
    $recentPosts->the_post();

    the_title();

endwhile;

But if you want to use the loop like normal loop, you need to use $wp_query as the variable. Also, everyone uses the parameters directly to the class as a constructor.

$wp_query = new WP_Query(array('showposts' => 9, 'post_type' => array('mycustomposttype1',  'mycustomposttype2','mycustomposttype3')));
while( have_posts() ) : 
    the_post();

    the_title();

endwhile;