Why did Microsoft call the Xbox the 360 instead of the Xbox 2?

It may have sounded cool at first but did they not look at how calling it the 360 is going to look stupid in the long run.

Xbox 360
Xbox 720
Xbox 1080
Xbox 1440

You see it starts to look retarded as it gets into its 4rd and 5th generation hell even the 720 sounds kinda lame.
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