Actually a lot of coins are good now, if comparing Bitcoin and Ethereum it is clear that Bitcoin still far outperforms Ethereum from market share.It could be that someday Bitcoin falls and there is an altcoin that replaces it or it could happen that the price of Bitcoin reaches a price of "0".

Currently the Ripple is an interesting coin, because when the price of Bitcoin and Ethereum falls the price of Ripple tends to be stable and also rise. We cannot determine who is the best because they have different characteristics. But for now or a decade ahead Bitcoin will still be number one.