Wordpress - get_results using wpdb

global $wpdb;

$result = $wpdb->get_results ( "
    SELECT * 
    FROM  $wpdb->posts
        WHERE post_type = 'page'
" );

foreach ( $result as $page )
{
   echo $page->ID.'<br/>';
   echo $page->post_title.'<br/>';
}

You have a slight misunderstanding:

When calling $wpdb, you get a list of properties that contain the core names of the tables:

// The custom prefix from wp-config.php
// only needed for custom tables
$wpdb->prefix

// Tables where you don't need a prefix: built in ones:
$wpdb->posts
$wpdb->postmeta
$wpdb->users

So your final query would look like this:

$wpdb->get_results( "SELECT * FROM {$wpdb->posts} WHERE post_type = 'page'" );