Read this to find out how to calculate the import duty for game consoles Link hidden: Login to view.
Your best option is probably to contact Customs and ask them to give you a binding tariff. This means you'll know exactly what you are paying and it won't be open to interpretation by Customs officials at the time of import.
As for selling the games worldwide, all shippers like UPS, Fedex, USPS etc act as brokers and take care of Customs for you. You can either put a note in your listing description saying international buyers are responsible for paying any duties or you can build them into your cost.
A great resource is Link hidden: Login to view. If you are a registered member you can use the Estimate Duties and Taxes tool to find out what duties will be to another country. You should also have a close read of restrictions for the countries you plan to send to - if the import duties are too high or the item is restricted, you would be better off excluding people from these countries from bidding on your item.
Hope that helps :)