Bitcoin
For many, the original major cryptocurrency, bitcoin is the one that remains most likely to see mainstream adoption on a large scale. While there is no single authoritative list of companies around the world that accept digital currencies like bitcoin, Coin Telegraph suggests that 54 major companies currently accept one or more digital currencies. Of those, just two don't accept bitcoin. In this way, bitcoin has outpaced all other digital currencies currently on offer, and in this way it is the most usable digital currency in the mainstream business world at this point, at least when it comes to payments.
Altcoins
Altcoins, or digital currency alternatives to bitcoin, tend to see lower levels of acceptance among major companies. Coin Telegraph suggests that, compared with 52 major companies accepting bitcoin as of this time, only 25 accept litecoin, 13 accept ethereum, 14 accept bitcoin cash, 15 accept dogecoin and 12 accept monero.