The term unicorn did really made a fuss. But what is really the similarity of bitcoin and the unicorn. The unicorn is a kind of horse with wings, a mythical horse like no other. Bitcoin on the other hand is the king of cryptocurrency like no other. Unicorn can fly and soar in the sky and so is bitcoin it can soar to the moon during bullish moments but just like the unicorn who gets back to land after it fly bitcoin also has bearish moments.
But seriously, bitcoin is a unicorn because bitcoin is legendary. It has made greater feats in the cryptocurrency world and up to now is still the king and the leading cryptocurrency in the world. It has brought about big changes in the financial economy and has brought many people into riches in just years of holding. In short bitcoin is the mythical cryptocurrency that is loved by many.
Isn't the horse with wings is called pegasus? Unicorn on the other hand is a horse with one horn in the middle of its forehead. It is a mythical creature that can only appear in a person's dream or wild imagination. Though I am a bit confuse about being Bitcoin a unicorn since as what Wind_fury stated it is out of reach while Bitcoin is already within reach.