Coinbase has grown tremendously and now offers users over 80 different cryptocurrencies, including popular cryptocurrencies like Ethereum and Dogecoin, with over 2700 employees around the globe.
Kucoin shouldn't be counted out of the picture when determining what the best cryptocurrency exchange is. That being said, Kucoin is not licensed to operate in the U.S., meaning that you can't use traditional payment methods to deposit money into Kucoin.
Gemini is one of the only cryptocurrency exchanges globally that is regulated. Not only is it a significant player in the exchange space, but you'll also be pleased to learn that nobody has ever successfully hacked it.