The best DEX is ViteX built on Vite (this is DAG project, like IOTA but with smartcontract). And they share 90% of revenue from trading fees to token holders (10% for owners). And this DEX is for multi blockhains.
Have you heard about uniswap, it's a dex exchange, currently lots of coins in there are doing x5 - 100, to me its consider the best Dex for now because it's really easy to navigate through, lots of people have been made awesomely rich from that exchange
Uniswap only supports Ethereum tokens, so it's really not my cup of tea

The volume is growing though, the same can be said about other DEX's such as Blocknet's DX platform, and Bisq.