If I were to hodl only 1 coin for 10 years, I would not choose any altcoin. I think altcoin can go disappeared at anytime.
I would choose either ETH or Btc. I prefer bitcoin as it is the parent and the beginning of everything. It would not go disappeared anytime soon.
In 10 years, it may go to 100K. We never know.
I would agree with you. But at the same time, I have to remember you that ETH is also an altcoin. It is over-priced, and after the decimation of the ICO market its future is looking more or less uncertain. I would rather limit my choice to Bitcoin (you can add Bitcoin Cash if you want).