Let's be more neutral to be more objective, "Bitcoin and ethereum are becoming kings in their own space".
We have several functional classifications in this regard. Bitcoin is simply a means of payment that offers the highest level of network protocol integrity with continuous improvements to be as effective and efficient as possible. Ethereum's function is more oriented towards ecosystem infrastructure, where instead of choosing Bitcoin, dapps developers prefer Ethereum which can clearly facilitate their business.
The more varied the innovation of the crypto business, the more coins will come with their own characteristics and the first one is usually the "King".