Buy bitcoin as always this is the best crypto that everyone should have. And as you plan of holding for years, what you need to know is bitcoin is good at it. Many bitcoin holders in the world are existing and everyone does prepare to have their own bitcoin that's good for holding for years.
If you are able to invest your fund bigger you can invest on bitcoin since its price is higher than other cryptos. I do agree that bitcoin has the potential to grow double the value in the chart what we are seeing now.
As you said many people holded their bitcoins in the hardware and holding it 60% percent of the coins what is mined already. Balance bitcoins only in the circulation so that is the reason always have the potential to find the bump more in the chart.
Other than bitcoin, you can prefer the ETH, ETC, LTC, DASH, ZEC, XMR and XRP. These will increase in the value or even mining difficulty also increase on these coins.