2018 may be a market that has been falling, holding a better choice for your bitcoin in such a market.
I think Cryptocurrency sprang up everywhere like Bitcoin because this is the first of every peer-to-peer network, providing coins and trading platforms, also has its own blockchain, its current market capitalization, its price, its scalability, and its popularity is hard to ignore. and will stay for a long time. so the advice I would give is that any crypto currency that is not only there to serve as a coin or a trading asset but provide more services will definitely survive and you can invest in it in the long run.
I think you should put your money in bitcoin itself as it have dropped so much in value from the start of the year 2018, so when it gets backup then it will be a more than 2x gain for the investors, so it's better to invest in Bitcoin than in other crypto. And even there have been times when bitcoin increased in value and other crypto were still of the same price so that would be dangerous if you invest in altcoins.