Make new user have Editor role.

Stick the following snippet into a php file in your mu-plugins dir:

<?php
function ds_new_user_meta($blog_id, $user_id) {
 add_user_to_blog($blog_id, $user_id, 'editor' );
}
add_action( 'wpmu_new_blog', 'ds_new_user_meta', 10, 2 );
?>

http://wordpress.org/support/topic/how-do-i-change-the-default-administrator-role-to-author-for-new-users