Bitcoin being the fast brought with it couple of advantages :-
- Well-known, the word "Bitcoin" has been thrown around for almost 10 years now, and it is still alive and one of the most valuable digital asset
- Network effect... most cryptocurrency adopters started with bitcoin and also attracts the most serious audience and holders
- When Bitcoin was launched it influenced a lot in terms of philosophy and economics of a digital asset, spawning new ideas and setting the tone for decentralization

In terms of value, money is very much a function of its network effect.
For a new cryptocurrency to pose a serious contender to Bitcoin, not only the alternative needs to be better but Bitcoin probably would need some defects
Simplicity of Bitcoin purpose also reduces the possibility of defects which makes it less popular than the alternatives