Microsoft: $21.2 Amazon: $20.4B
From [1]. That includes Office365 revenue[2]. Excluding that, Azure is about 1/3 the size of AWS[3]
[1] https://www.zdnet.com/article/cloud-providers-ranking-2018-h...
[2] https://techcrunch.com/2017/10/30/aws-continues-to-rule-the-...
[3] https://www.srgresearch.com/articles/cloud-market-keeps-grow...