Yes and because of following factors:
1. Majority of trading platform use Bitcoin as the primary coin that enable one to buy any other coin.
2. Block chain technology enhances its security wih the number of entries it has. Since Bitcoin is the first and mostly traded platfom, it becomes more and more secure as time passes by.
It will be dominant up and untill everyone starts trading in crypto currency. If everyone start trading in cryptocurrency just because of preferences and belief system other coins will also be used. Just like how we have various religions in the world even if Christianity is the most prevelant.