There are many coins which are better than bitcoin in many aspects. Some are faster than bitcoin and some have good scalability, even some have almost negligible transaction fee but they all have these features because they are not being used at the large scale at which BTC is being used. BTC is used in ICOs, it is also used for trading on all the exchanges which are present at the time and that's why it is slow or transaction fee is high. So BTC dominance is going to vanish easily. Of course some coins can supercede bitcoin in terms of  price per coin or even market cap but they can't dominate the market like bitcoin.