they already competed, but Bitcoin's marketcap is more away than Ethereum's marketcap. Bitcoin is 6 trillion and Ethereum only have 1.1 Trillion. The closest competition right now is Ripple and Ethereum for battling rank 2 because their marketcap are very close to each other, there's a day Ripple got the rank 2 when it pumped and Ethereum dropped rank 3 but after many days Ripple got dumped again and Ethereum regains its rank 2.