Leader: Amazon Web Services

More than a decade after pioneering the market, AWS remains atop the IaaS pack, both as a go-to cloud for most types of organizations, and a thought leader for integrated IaaS and PaaS.

Amazon's most-profitable division closed out last year with a revenue run-rate exceeding $20 billion.

"It continues to aggressively expand into new IT markets via new services as well as acquisitions, adding to an already rich portfolio of services. It also continues to enhance existing services with new capabilities, with a particular emphasis on management and integration," Gartner noted.

But it's best to work with a systems integrator when taking on large digital transformation efforts, Gartner noted.

AWS is "still adapting to the emergence of meaningful competitors." And competitors copying its ideas "sometimes have the opportunity to improve on the implementation or service construct."