A possible scenario is this: Cardano, PRiVCY, EOS, Stellar and the like. It is only if these projects will develop its platform and on.
In this year 2018 I think the best altcoin is ethereum because this is the one who fluctuated in its prices ,this coin is more demand for investors because the amount we invest or buy in such coin has a good returned of profit.
ethereum has until now become the best altcoin,
although at this time ethereum prices were down but there were still many people,
I am sure that over time ethereum prices will rise
Ethereum is far to be one of the best altcoin. You just claim this because of ethereum rank on coinmarketplace but forget about it