Top 500 is still too wide and in my opinion not all of them are good to invest, also there are a lot of project are using fake volume to get more investors. I think, coinmarketcap rank can't be a good factor to invest in projects.
Of course, there are lots of coins on coinmarketcap which need their volume and cap to be corrected as it mislead some investors. Sometimes it takes time for coinmarketcap to update such information. Although investing in coins already on coinmarketcap like the first 100 coins is not an assurance of gaining profit, it helps the investor to escape new projects which are likely to turn out to be scam.