Custom WP Query from meta_value stored as serialised array

If you’re inside the while loop, use get_the_ID().

// returns an array as this is a multicheck field in Magic Fields 2
if(get_post_meta(get_the_ID(), 'services', true)){
    $services = get_post_meta(get_the_ID(), 'services', true);
    $services = maybe_unserialize($services);
    // foreach item in the array
    foreach ($services as $service) {
        if ( sanitize_title($service_title) == sanitize_title($service) ) {
            echo '<p>' . esc_attr($service) . '</p>';
        }
    }
} else {
    //No services set
}

Check this.
Btw, you can set an array as a meta field value (but via code using add_post_meta, not the via post meta box on post edit screen).