ETH platform has a broader potential (ICO, apps, etc ...) and according to the data from the last week, 70% of all crypto transactions are happening on the ETH network today.

ETH/BTC price ratio long term will be linked to these 3 factors:

1) Total number of ETH coins in the circulation when the mining stops
2) Overall use of the ETH network for new applications and services
3) Number of transactions on BTC network