If you want to make an archive page for multiple post types you want to show the title of the post type first. You can do that by using:
<?php post_type_archive_title(); ?>
For showing the content you can use the normal loop. But if you want to modify the loop by query_post(); you have to make a variable for ‘post_type’ that automatically fills in the right post type name.
You can do that by using the get_queried_object(); function:
<?php $obj = get_queried_object(); $post_type = $obj->name; $args = array( 'post_type' => $post_type, 'orderby' => 'title', 'order' => 'ASC', 'posts_per_page' => 20, ); query_posts($args); // And then the loop ?>