Nope, its not. Bitcoin is useless without altcoins. I think the reason of why the price of bitcoin is rise is because of altcoins. For my own analysis, as you can see in the graph from 2014 upto this year 2017. The bitcoin price is continue increasing and the altcoins is increased in numbers. Therefore, the many altcoins made the more bitcoin price increase.
This does not make sense, and most of the time it is the other way around, you can buy bitcoin with fiat, but can you buy other cryptos with fiat? Most of the time the answer is not, in order to buy alts you need to use bitcoin, so altcoins grow because of bitcoin and no the other way around.