get_super_admins()

function get_super_admins() {
	global $super_admins;

	if ( isset( $super_admins ) ) {
		return $super_admins;
	} else {
		return get_site_option( 'site_admins', array( 'admin' ) );
	}
}

$super_admins = get_super_admins();

echo __( 'List of super-admin users:', 'textdomain' );

if ( ! empty( $super_admins ) ) {
	echo '<ul>';
	
	foreach ( $super_admins as $admin ) {
		echo '<li>' . $admin . '</li>';
	}
	
	echo '</ul>';
}