I would rank a currency by [ trading volume x price ]. I think this will be more accurate to its actual usage.
In competition with all other crypto currencies which are there in this world, bitcoin is surely the best crypto coin and that there is no other coin which is that much beneficial as bitcoin is and is the top rated crypto coin too. However, when it comes to that of other regular currencies, we cannot claim bitcoin as the top rated currency because so far, it has not been declared as the legal currency.