Can you suggest me which one is best Altcoin coin hold for 2018? 
Ethereum
Litecoin
Neo
Cardano
Iota
EOS
Ripple
This altcoins are my currently hold for long term and I advise you should make a research before invest, don't just make decisions on what do you heard the other people.
Your holding altcoins are definitely good for long term investment, and most of them I also currently hold like Ethereum Litecoin Neo Ripple and Cardano. And yes you have a point don't just put your money in a coin, before that you should do a research.