After 8 years of clear dominance, easily having between 50% and 99% volume of the total cryptocurrency market, today bitcoin's volume is perhaps 30% ( haven't calculated ) of total volume, on par with eth's volume.
http://imgur.com/a/1iU3UCMC forgot in the BTC volume maths that any exchange on a ETH/BTC pair is also volume for BTC.
It's the same for all the other pairs that include BTC.
We are far away from parity atm