Certain, newer pieces of some of these services, such as the Azure Active Directory service at the heart of Office 365 and some of the newer, complementary Xbox Live services are hosted on Azure. But the core Bing, Office 365 Commercial and Consumer offerings and Xbox Live services are not hosted on Azure. (same article as above)
It seems like amazon is using an "all in" strategy which seems to be working out pretty well. They first focused on porting the entire amazon retail website onto AWS which I believe they completed in 2011. They also went "all in" with the service oriented architecture for AWS. Both of these have paid off quite handsomely.
Granted, that hasn't always paid off (we all know how the fire phone turned out), but the wins have definitely made up for the losses.
http://9to5mac.com/2016/04/11/apple-icloud-in-house-inspur/