in my opinion, the most secure coin is the ethereum. anyone has been no more doubtful about its potential move and these stages construct in the market. for personally, the coins the more I recommend, or maybe you can see a list of the coins is good at CMC.
Yes no doubt that Etherium is the best altcoin in current time for investment, but i think that there may be some other altcoin which may also be good and secure for investment, but i think that the only need is how to recognize it. I think that if we study the market regularly we can find our some other altcoin, which have good potential and are also too much trusted and reliable for investment.