If other altcoins can increases their value, I think these altcoins still have chance to become famous as Bitcoin at now. So, we can say Bitcoin will be the best cryptocurrency has most users, Ethereum or other altcoins still can overpass any time.
A few months back, Ethereum used to give stiff competition to Bitcoin. A lot of experts even predicted that the market cap of Ether would soon overtake that of Bitcoin. But during the past few months, the Ether exchange rates have gone down, with respective to Bitcoin. It is not the fault of Ether though. The uncertainty regarding Bitcoin Cash vanished two months back, and it gave a major boost for BTC (and a corresponding decline for Ether).