Been thinking about this for a bit as to possible reasons for the Xboxone name as their 3rd system, I know there is the PR thing that it is the one system you need under your TV (altho it doesn't have backwards compat so you at least need a 360) but yeah I will use my amazing skills in MS paint to show another reason for the 3rd system having the number 1.
As we all remember the first console didn't feature any number, just being called the Xbox or after the 360 came out was referred to as "the original Xbox" but then the 360 launched after that, an odd number to begin with when adding numbers to the system, but it rings off the tongue quite well but 360 is another thing, a circle! or a 0 which was what made me think if you look back at the system names and instead think of them as the Xbox, the Xbox 0 and now the Xbox 1 it almost makes sense... (to me at 8am having been up all night with flu)
Or have I just lost my mind...
edit - my tagged launch "360" game names supports my theory! both tagged with Zero and being xbox360 exclusives.
Fancy hearing me on an amateur podcast with friends gushing over one of my favourite games? https://youtu.be/1I7JfMMxhf8