I think that bitcoin will always control the marrket. New coins come every day but u can see when Bitcoin price drops the altcoins also go down.
Actually both coins are required to control the market, but bitcoin stands one step ahead than all the altcoins. Bitcoin is higher value coin but altcoins consists of more low base price coins and also coins like bitcoin cash, Ethereum are slightly high price but comparing bitcoin very less. So I think both the coins results in the market fluctuations.