As of now, there is no altcoin that can replace bitcoin. It had been the most successful crypto, people see bitcoin as the main cryptocurrency. It is too far from reality for ethereum to replace bitcoin at the current state since bitcoin dominates the market.
It seems like Bitcoin will always rank first because bitcoin is the parent of all coins in my opinion, and ethereum is unlikely to be the first rating seen from current prices quite far from the price of bitcoin and bitcoin is still used by many people as an investment