I would always prefer to invest in hottest coins in 2019 BTC and Ethereum. Ethereum is for the long term investment. Another coin rather than these is vaxanium.
Up to now, ethereum still does not show any value for long-term investment, almost value only knows to turn and go down, even when the market shows signs of recovery, ethereum still once again breaks those signals and goes down, it is not the hottest investment, other altcoins are similar. 2019 is probably a time for bitcoin to prove its sustainability over time, it is the hottest coin, the value has not dropped and still has growth, does not allow altcoins to have a chance to show off, the stage in 2019 is probably just a solo show of bitcoin.
The thing is by the time ethereum show some signs that it can be a good investment you are going to lose a substantial amount of the growth, so what you need to do is to buy a coin before those signs are present but that is severely undervalued and there is no coin in the market that gives me more confidence that it will grow in the long term than ethereum, in fact right now is having significant gains and it is likely this will continue during the next days.