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.