There are probably other coins that are as good, or almost as good (or even better? I'm no expert in the technical details) as Bitcoin. But Bitcoin is legendary - meaning it is the first, it is the most known, and it is by far the most used. It has also gotten proven to work a lot like gold (protection against inflation) And currency is pretty simple. If people decide Bitcoin is worthy, then it is worthy. The only question is how the regulators, states and banks will fight it.