The cryptocurrency market is tiny at the moment so the reality is, the dominance of BTC is irrelevant in the grand scheme of things as it's only relevant to today's market. Then when you consider the fact that today's crypto market is made up of mostly crypto enthusiasts who have a sentimental attachment to BTC that is based on its current dominant value and market share. In other words, for these reasons, the current market's community mostly believe that BTC is the most important cryptocurrency.
However, this will have very little bearing on the crypto market in 5 - 10 years time once the masses are using cryptocurrency. When real mass adoption arrives, the market will be 100 times bigger, probably a lot more are the majority won't have the same sentimental attachment to BTC as the early crypto adopters have. The masses will make their own mind up on which cryptocurrency is used the most and they WILL do their research. Granted, most of this research will be done by the media but ultimatly, it will be the masses who decide and not us.

A very important consideration that can't be overlooked and could potentially be the most important variable is the fact that, for the first 2 - 3 years of mass adoption, most transactions will be small, low value transactions. The masses will need time to learn to trust this new money and they won't be happy about high transaction fee's.

They will also want peer to peer transactions so I doubt the BTC lightening network will attract the masses.

Finally, the masses don't like to think too much.They want things to be easy and quick. This is why Amazon rose to become what it is today. It provided the easiest and quickest shopping experience at a time when most websites required 7 or 8 clicks. The reason I mention this is because you can't underestimate how important the web address of bitcoin.com is. Most people consider the exact match .com address as the official home for a business.

These reasons all point to Bitcoin Cash earning the title of Bitcoin when the masses arrive creating a MASSIVE change for the entire eco-system.