How do you define "successful"?
There are two ways of looking in to it. The first is in terms of market cap. This one will be easy for Bitcoin Cash. Already their market cap is fluctuating between $8 billion and $10 billion, and they have the potential to overtake Ethereum, or even BTC itself.
It's not that simple. That's the same logic that says Ripple's market cap is meaningful. When the vast majority of supply cannot be moved/liquidated, the market cap is meaningless. Let's wait until the chain is stable and markets are opened on the bigger exchanges. Then we might begin to see more realistic pricing.