I believe we might see something that will replace Ethereum within a year. I am betting on ICON or WANCOIN. But no one knows. Ethereum has grown alot although you can make profit there but it isnt like the new altcoins that can make you more profits in the future. Icon and Wanchain is a good pick i expect a massive gains after this two alts especially wanchain is the most awaited alt to be added in exchange while icon was still cheap in my opinion. I will personaly hold viberate for more than a year as i belive in project. Coin is still cheap and the devs are sticinkg to road map so i have nothing bad to say about it. you can read more on it here:
https://www.viberate.io/Normally, I would answer Bitcoin for a long-term investment like this. But this time I will answer Ethereum only. Why ? That's because Ethereum has a small fee, unlike Bitcoin. Currently the price of Bitcoin has become very high, so the fee also comes high and to do transactions using Bitcoin will be more difficult. Maybe in the future there will be more sophisticated technology to solve this problem. But for now, Ethereum is the best choice to invest Altcoin and cryptocurrency. Or maybe you have better advice to invest in some other crypto I do not know yet.