you are asking a couple of different questions.
a platform that lists all the altcoins, (and based on your last statement) all the new coins that are released everyday is a shitty exchange. and it is called Yobit. it is not at all trusted! because you need to vet the coins you add first.
cryptopia is actually a good place, the owner seems to be serious enough and will do what they believe in. for example they removed ethereum from their platform and kept it like that because they had pretty good reasons and stuck to them even with all the high volume and their users asking them to.
but if you want a big exchange with high liquidity and a more trusted exchange then use poloniex or bittrex.
and if support is important to you then know that polo support sucks.
Sorry i meant a platform that has latest coins for trading, I know coinmarketcap displays all the coins.
I am already with poloniex but they don't have some coins that I wanted to buy. Haven't traded anything yet though hah.
Didn't try bittrex yet.
Thanks for the help