My single liner answer is Top 20 coins on coinmarketcap are good for long term investment except XRP because SEC has filed lawsuit against it due to alleged irregularities committed by its management. My most favourite coin is Polkadot which has shown tremendous growth during the year 2020 because it is better alternative of Ethereum due to speedy network and lower gas fee. It will continue growing as new projects are using its network to create new coins and DEFI projects.
The top 20 coinmarketcap mostly includes old coins and their price growth is limited to a maximum of 300 percent. But from the new coins, you can expect much more profit, because their capitalization is still very small compared to TOP. A good example to my words is WazirX (WRX), the price of which increased after the dump by 20 times.