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.
Yes. That's our way to avoid those scam and also to avoid losing our money. Some people lose their money because they are just invested on it without knowing about the coin. We should research always to avoid those scam.