Bitcoin,Ethereum and Neo is what must come in mind when considering long term investment.
for me today the most promising coin is ethereum, But if you analyze a stellar, then lately this platform has shown quite good results, Even despite the poor state of the market.
The most promising penny is the ICNQ penny, the penny you're trying to sign underneath your account, I'm also analyzing and planning to invest in this penny. I think they will grow when their projects are completed. So I will buy and hold them for a year