##Use a pattern

The general principle is fine, though it won't handle plugin routes (which I assume isn't a problem)

However instead of a loop (and therefore defining 6 routes per controller) a parameter for the controller name can be used which will be more concise and likely overall more performant. The code could be rewritten like this:

// Define a home route
Router::connect('/', array('controller' => 'pages', 'action' => 'displayHome'));

// Generate a regex-like controller name pattern (e.g. "posts|comments|users")
$controllerList = App::objects('controller');
$controllerList = array_map(function($c) {
    return Inflector::underscore(substr($c, 0, strlen($c)-10);
}, $controllerList));
$controllerList = array_filter($controllerList, function ($c) {
    return $c !== 'app'
});
$controller = implode('|', $controllerList);

// Define normal routes
$params = array('controller' => $controller);
Router::connect('/:controller', $params);
Router::connect('/:controller/:action', $params);
Router::connect('/:controller/:action/*', $params);

// Define admin routes
$params += array('admin' => true, 'prefix' => 'admin');
Router::connect('/admin/:controller', $params);
Router::connect('/admin/:controller/:action', $params);
Router::connect('/admin/:controller/:action/*', $params);

// Define catchall
Router::connect('/**', array('controller'=>'pages', 'action'=>'display'));

In this way there are 8 routes in total, no matter how many controllers there are in the application.

Use a pattern

The general principle is fine, though it won't handle plugin routes (which I assume isn't a problem)

However instead of a loop (and therefore defining 6 routes per controller) a parameter for the controller name can be used which will be more concise and likely overall more performant. The code could be rewritten like this:

// Define a home route
Router::connect('/', array('controller' => 'pages', 'action' => 'displayHome'));

// Generate a regex-like controller name pattern (e.g. "posts|comments|users")
$controllerList = App::objects('controller');
$controllerList = array_map(function($c) {
    return Inflector::underscore(substr($c, 0, strlen($c)-10);
}, $controllerList));
$controllerList = array_filter($controllerList, function ($c) {
    return $c !== 'app'
});
$controller = implode('|', $controllerList);

// Define normal routes
$params = array('controller' => $controller);
Router::connect('/:controller', $params);
Router::connect('/:controller/:action', $params);
Router::connect('/:controller/:action/*', $params);

// Define admin routes
$params += array('admin' => true, 'prefix' => 'admin');
Router::connect('/admin/:controller', $params);
Router::connect('/admin/:controller/:action', $params);
Router::connect('/admin/:controller/:action/*', $params);

// Define catchall
Router::connect('/**', array('controller'=>'pages', 'action'=>'display'));

In this way there are 8 routes in total, no matter how many controllers there are in the application.