Well of course, you can't compare Bitcoin with Ethereum for instance, but you could do it to other altcoins that are meant to be used as a currency such as Litrcoin or Dash.

Well for my last point I'm not talking about volume but true market capitalization, allow me to illustrate: there is $100 billion in BTC and only BTC. You create an altcoin that nobody wants but gets somehow listed in a random exchange with the pair Xcoin/BTC. Out of thin air, the marketcap went from $100 billion to $100 + something. That something is not usd. No new usd entered the economy, instead the value of that coin is being calculated based on what a BTC costs, but it actually is traded via BTC, which means that cap is kind of imaginary. Trying to find a medium article on that I read once.

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