@kuroi : phew...finally i found out the issue, and no, it's not because of the incomplete upgrade process. I have to read featured.php code to find out why featured products do not list the product.
It turns out there's this code that prevent this to happen:
You see, I don't want to display the "add to cart" button in product listing page. I read in this forum that I should set this option from Catalog > Product Types > Product - General > Edit > uncheck "this product can be added to cart".
// do not include things that cannot go in the cart
$not_for_cart = $db->Execute("select p.products_id from " . TABLE_PRODUCTS . " p left join " . TABLE_PRODUCT_TYPES . " pt on p.products_type= pt.type_id where pt.allow_add_to_cart = 'N'");
When I check back this option, I can see the featured products list
Anyway, Is there any other option for me to keep displaying the featured products list without setting the "added to cart" to true? If there's none, I can just edit the sqlquery above which I prefer not to.