Bitcoin was first digital coin so I don't think it's value will be low or will beat it by other coins in market it's most traded coin as now in market cap. And no other coin has too much popularity like bitcoin so it will never happen.
People still do not trust crypto currencies very much, so they often invest in reliable assets, and bitcoin, in their opinion, is most known and reliable. If the crypto currency market changes, it will become more predictable, then perhaps bitcoin will cease to be the main coin of this market.