Cromen Bitcoin, for me the best alt for a long term investment is ETH, but also past ETH for the long term I keep the following coins: LTC, BNB, EOS, Vite, TRX, but everyone has to choose coins for their own investment.
Whatever coins you choose make sure to do research before buying to understand the uses and if its good for long term holding. Its easy to pick or suggest a coin but its a must that we have our own knowledge in the particular coin so we wont blame anyone but ourselves if something went wrong.
IMO top alts are the best when it comes to long term.