There have been hundreds of virtual currencies introduced both before and after Bitcoin. However, Bitcoin remains the most popular of all of them. While it has some obvious advantages over many of the other schemes, it would be speculative to try to explain exactly why it has succeeded where others have failed. However, regardless of the reasons, it has a strong enough foothold to last for a very long time.

My personal opinion is that Bitcoin is popular because it makes money more flexible, and enables people to take absolute control over their money - in the same way that the mp3 standard enabled them to take control of their music.