Are you on about which exchange allows the trading of the widest range of crypto-currencies or which exchange actually holds the biggest amount of coins in total? The exchange you listed are probably the biggest ones out there, so I'm not sure you will find a bigger one.
Looking for an exchange that has the widest range of cryptos available...all that I mentioned are good but not all coins are available there...
Bittrex and cryptopia.co.nz have the widest range of cryptos from what I've seen. If you are looking to trade ERC20 tokens you'll likely have to use etherdelta, as only few of them are listed on centralized exchanges.
If you're looking for specific coins to trade, why not check on coinmarketcap which market covers the most alts that you are interested in?