It's actually a different question (sometimes called "the even harder question" or "the vertiginous question"), but if you have ever asked yourself the question of "why am I me and not someone else", the gap in our understanding of consciousness becomes clearer.
To use the same example: If there was a spreadsheet simulating every neuron in my brain, which one would be "I"? The original "I", or the spreadsheet?
Note that this question becomes meaningless if you change "I" to something else, so "both would be me" is not a valid answer. There is only one "I" (since I can't be experiencing the world from two sets of eyes, one organic and one spreadsheet-eyes, simultaneously), so I have to choose one of them.