I have a lot of trouble finding answers to questions like these on the internet, may be it's because it's hard to explain. But let me give an example, Imagine I create a website better and more useful than Twitter, in every way, will it become any popular? considering the amount of popularity Twitter already has?

I understand people will not immediately flock over and just leave Twitter, but I don't want to beat Twitter but just make my site famous and successful in general. And again Twitter is just an example, I am trying the figure out the principles in web2.0 success, through this hypothetical question.