I think BTC & ETH are quite good.

BTC is a "King of cryptocurrencies", the first of crypto in the world. BTC is very common (dominance usually >50%). BTC use as the main currency for payment, trade. If my opinion, BTC like a "gold", to hold, hold and hold.

ETH is good, too. With the smart contract, every transaction is clear. The speed of ETH is fast and the fee quite cheap.
Many token build base on ETH blockchain, so I think ETH is very important. However, this is also one weakness of ETH. Because of many token builds on ETH Blockchain, the ETH blockchain easy to jam. So, in the future, ETH need improve your blockchain, like add sharding on this.

So, it is my opinion.