Not knowing much about the console...
Are you saying the console has a 9 pin serial connector that is designed to plug into a PC and you want to be able to convert this so it uses a USB connection instead? If this is the case then you don't need Arduino as you can buy RS232/USB adaptors. Some are better than others so it might be worth looking for reviews.
Another option using Arduino would maybe be the Arduino Micro as it has native USB support and a USART port you could connect the console to (via a suitable adaptor). The Micro's USB connection can look like a serial port to the PC or it can also mimic a USB mouse/keyboard/joystick.