To be honest, Bitcoin enjoys first mover advantage. Because we have many altcoins available in the market which are technically more advanced than Bitcoin. But no altcoins was able to move out Bitcoin from the first position.
I believe the biggest strength of Bitcoin is its community. No other coins have such a strong community like Bitcoin. The community is global in nature. If some old coin is able to pull together a community bigger than Bitcoin, will surely over take Bitcoin. But for now, I do not see it happening!
If any coin has not been able to replace it from first position, it does not mean it will not happen in future also. I believe the biggest strength of Bitcoin is its community. No other coins have such a strong community like Bitcoin. The community is global in nature. If some old coin is able to pull together a community bigger than Bitcoin, will surely over take Bitcoin. But for now, I do not see it happening!