The British Empire owed its success to many factors. One key to its success was its efficient taxation system. While this angered colonists, British taxes funded the realm, and the empire did not become a drain on the nation's resources until after WWI; this is truly remarkable given the size of the empire.
Another factor in the success of the British Empire was the size and success of its navy. The British navy defended British trade and possessions all over the world. The rise of the British Empire dates from around 1588, when the British navy under Sir Francis Drake defeated the Spanish Armada. Without a powerful navy, Britain would not have an empire and would have been susceptible to invasion.
Another factor in the success of the British Empire was its willingness to send people to possessions in order to truly possess them. Rather than fight religious dissidents at home, Britain provided a way for them to not be a nuisance to the Church of England and still contribute to the empire's resources. In this way, Britain was able to turn its political and religious liabilities into assets. These assets also came in handy when it came to defending the realm, as colonists from North America were often more than willing to attack French and Spanish possessions in the name of the Crown.
All of these factors can be summarized as Britain simply being better at managing its possessions than Spain and France. Britain also had the navy needed to supply and defend its colonies.