So, with Microsoft breaking the naming convention of their system, we have to come up with a name for this thing again. Nobody really wants to spat out the "Original Xbox" every time we refer to it. Saying just Xbox will make me think of whatever Microsoft box is out now. So what do we call it?
This is now called the First Box
. No need for an X. Just the First Box. It's short and to the point. It can be used for reminiscing. For example if you are talking about the first time you experienced Xbox Live you can say, "I had it on the First Box." If you are talking about the first time you played Forza you can refer to the First Box. It all works out just fine.
Just be happy the naming conventions of game consoles are not as bad as DSLR cameras.