Are you talking about forex brokers? Because maybe you are talking about altcoin exchanges, but no one calls them as "brokers" but in fact, they are almost the same.
is there any list of best available crypto broker?
SimpleFX was one of the best brokers that was accepting bitcoins and other altcoins, but now it has become scam and nobody is using it.
They came up saying that they had a regulation on their services from the US and they had to cut some losses from their investor's balances, and that is why they cancelled all the withdrawals and some trades that were opened at that moment.
Markets.com is accepting bitcoins too, but i do not know if they are still accepting it.