Not so long ago, CMC was under fire for ranking exchanges based on trading volume alone. I was observed that so many shady and scam exchanges would manipulate the trading volume to be on the top ranking.
How are you going to ensure that the reported data does not manipulate the ranks? What other parameters will you be looking at, if any?
Unfortunately, Coinmarketcap was a mess at the time. Since then, I have stopped visiting it myself.
On CMC, there was (and still is) a lot of shady exchanges with completely unreal volumes. From what I can see, here are only a few, but trusted and well-established exchanges:
Binance
Coinbase
Huobi Global
Kraken
Bitfinex
Bittrex
Poloniex