Google indeed seems the strongest competitor now for AWS, but there are far more providers who compete - see a comparison: https://www.cloudorado.com/ . We just need to choose them to avoid monopoly or at least oligopoly.
All Google needs to do is innovate on tech, pricing, and marketing. They can chip away at Amazon's lead. Google does not need all of Amazon's customers, just some. And, it's a growth industry.
Google is more a service company than MS, and I believe it is more experienced in cloud technologies.
http://www.datamation.com/cloud-computing/microsoft-and-goog...
Azure is slow, expensive, poorly designed (network and SSD designs are just bad), and the real slap to the face is that the management UI Is worse than anything from Windows 8.
Without vocal early adopters and evangelists in the wild, it is impossible for AWS to get to its current stage. Those people may not bring in that big of money, but they are willing to take risks and eagerly to give feedbacks, sharing their experience and come up with their own solution around it. The feedback loop is enclosed in that way, and the service can evolve with it.
MS still doesn't hit that spot yet.