Ripple is a great competitor of Ethereum, in terms of coinmarketcap ranking, Ethereum and Ripple has been changing their ranking. On marketcapitalizing I think Ethereum has been consistent, but in crypto anything can happen, Ripple has the capacity in near future to turn the tide because they had being partnering with big organizations to boost the platform.
I think that the positions altcoins ranking whether by coinmarketcap ranking or marketcapitalizing (volume), is open to all coin/tokens now and in future.