Azure according to Gartner's magic quadrants
A useful summary:
With a unique cloud strategy spanning private cloud, public cloud (IaaS and PaaS), and SaaS, Microsoft is proud to be recognized by Gartner, a leading independent research firm, as the only vendor selected as a leader across this deep list of their Magic Quadrants for enterprise cloud workloads. This includes being a leader in Cloud Infrastructure as a Service, Cloud Storage Services, and Application Platform as a Service.