Unlike his competitor, Google is not working on software but on user experience. Their main goal is to improve user experience. For search engine, there is three pillars that impact user experience: 

1. Ease of use
2. Rapid response time
3. Pertinence of the result

A bit like Tiger Wood (who is also from Stanford like the founder of Google) they continue to invest heavily on the basic. They always try to improve and expand their search capability. It results in an always-greater lead over their competitors. 

Google understand human attention in human computer interaction. That’s why they came up with a successful add approach consisting in proposing a related link to what your are looking for inside the Useful Field of View (UFOV).

By the way, Google founders were student at Stanford HCI (Human Computer Interaction) group. The Stanford HCI Group is one of the most innovative and dynamic research center in the field. HCI is an instance of cognitive engineering focusing on the Human Computer Interaction. I believe because they have better capability and focus than competitor on what bring value to their customer, they will continue to make more money.  

I can only see them gain more and more value over the next few years.