Can you suggest me which one is best Altcoin coin hold for 2018? 
For me, it's still Bitcoin and Ethereum, these two coins control the market and the community, all the other coins just follow their progress, some top coins are just a forked of Bitcoin and using Ethereum smart contract although there are coins that can make you ten times profit but when it comes to stability, they are the two coin.
That is right, with these two coins, I am sure that we can hold this for a long-term and I am sure that we can make a profit too. But I think it still worth if we hold bitcoin only because we know that bitcoin price will increase higher in the long-term. And don't forget that the other coins will have the same opportunity to give a big profit for you.