It's the oldest, strongest and most valuable cryptocurrency and it deserved to be on a throne. Afterall, it took this place because of the users who suport Bitcoin through all this years and huge progress it has made.
On the other hand market is open and every other coin has the opportunity for success although I truly doubt that some other coin will ever achieve such success.
And this happens because most coins are just copying what other people are doing without really integrating any kind of innovative ideas to their projects that can make them better.