Bitcoin is still the mother of all coins. Ethereum is widely used but it doesn't have a good reputation as bitcoin. I use ethereum and I love it for low transaction fees compared to bitcoin but let's just accept the fact that bitcoin cannot be removed in top 1.
I think you overestimate bitcoin. It is popular and it is the main reason why it is #1. It has old technology inside and it has a lot of problems with growing.
Ethereum is working consistently on scalability and they know what to do next. And I don't mention that 90% of the latest projects are based on its Blockchain which means that it has a great potential in terms of future demand in ETH and gas.
So, I believe it is a matter of a couple of years for ethereum to become #1 coin.
But I don't exclude that it could happen that there will appear a new coin that will take major place.
The evidence is right in front of you that you are mistaken, bitcoin is the oldest coin but you are talking as if the developers are just taking a vacation or something, they have been updating bitcoin and we went through a major update with segwit and the lightning network, and this is why the market cap of bitcoin has been growing like crazy and what has happened to Ethereum, nothing the price moved a little and that is it.