Joystiq actually constructs an argument

Joystiq has actually done a well constructed and intelligent Article on Wii and why it doesn't compare to any other made-up name.

And to fill in their table:

• Wii
  Wii sounds like 'we,' which emphasizes that the console is for everyone. Wii can easily be remembered by people around the world, no matter what language they speak. No confusion. No need to abbreviate. Just Wii.