Both has got its own value. Dollar has a long back history which makes it more stable than all other currencies. Bitcoin has got a very small history, so I believe bitcoin and dollar should never be compared. Both grow on its own way as both were independent of each other.
Makes no sense at all we compare these two currencies as bitcoin isnt mainstream ,and its value total at the moment are around 7 bilion dollars the market cap of dollars are far away from bitcoin and its a number that bitcoin cant achive and wont achieve as they got a limited supply.