Like a video game system, its success is how many publishers make games/software for it. A game system could have the fastest CPU, the best graphics, the most memory, the best everything, but if there are no games for it, it's a failure. The more games there are for a game system, the more successful it is.

In terms of smartphones, why is Android a success? Why is IOS a success? Why is Blackberry not a success? Why is Windows Phone not a success?

Bitcoin is a success when people use it. Its monetary value doesn't mean much if no one uses it.