Many investors has achieved a lot of profits from Ethereum investment, because Ethereum still remain the best altcoin among other altcoins in the market. Now that many altcoins price is preparing to increase higher in the market, it will be favourable to use this period to buy more of Ethereum and other altcoins and hold for the bullish period to come before you can sell to make a reasonable income which is the expectations of every holders in this season. Investing half of your money on Ethereum and other coins like Bitcoin and apply long holding, I think it will help you not to experience failure in your investment in the future.
To me first choice of investment is bitcoin and if I have to choose an Alt then Ethereum is the best option. But keep one thing in mind that price of all Alts including Ethereum are tightly coupled with Bitcoin. Which means price will go up or down based on bitcoin price. You won't see Ethereum going to moon when bitcoin is going down or vice versa. Based on these facts I have restricted myself to Bitcoin.
Yes it all really depends on how Bitcoin moves and that's why Bitcoin is the king of crypto,
when talking about long-term investment I don't think anyone doubts Bitcoin because apart from being safe and well deserved it will also provide profit,
but certainly everyone has their own choice.