In the past there had been alts that surpassed Bitcoin in unit price, though not in market cap. But that isn't where all that ends. There's something that goes beyond utility or use-case of cryptos, for me that's trust. A lot of people have got that trust for Bitcoin. They can confidently put their money in it and peacefully go to sleep compared to others. By the way, there's a reason that makes Bitcoin stand alone while others are referred to as altcoins. Bitcoin is the only cryptocurrency that isn't referred to as altcoin. If any altcoin surpasses Bitcoin price, that won't be anything special and I don't think it will affect Bitcoin's relevance. The only thing I know that can destroy Bitcoin is if the 21 million scarce supply is changed to something more.