Top-20 coins in coinmarketcap, but some coins is very bad decision to invest. For example I hate ripple because it's a centralized coin and except for popularity , coin doesn't have future. In one moment this coin can become a scam .
And this is the biggest problem, many of the coins at the top of the market cap are not coins in which you would want to invest either, that is why many prefer, myself included, to only invest in bitcoin since we know it is the only honest coin that we have, it is harsh but it is the only solution I have found to the problem of choosing a coin to invest.