As of now based on my experience, its Poloniex and bittrex. Big volume and fast trading. many traders are transacting here and its very smooth. Though I do trade in kraken and liqui also, they are a good alternative too. C-cex is also fine but I have some not so OK experience especially on not so familiar coin. 
You can exchange your bitcoin for fiat in localbitcoins. Here you can find the trusted traders to sell your bitcoin for online bank transfers, paypal, moneygram payment and many more. You do not need to escrow person additionally to have safe trade in this site.
Apart localbitcoins, you can try polenix, yobit and Coinbase to exchange your bitcoins.