It is difficult to predict which coins will be in the top 15 list for the next 5 years, because no one knows what the future will hold, there will be new altcoins and new platforms like what?
Alt with the DeFi idea is still popular today, if there is an alt that has smart contract features like Binance which has a popular exchange platform and BSC network, then that alt will rise to the top but I can't give you any coin suggestions because there are many alts who can compete in the top 15 positions.