4. Microsoft

2016 revenue: $85.7 billion

2015 revenue: $88.1 billion

Partners applauded Microsoft for its recent $100 million acquisition of Hexadite as a way to boost its security offerings, and the vendor continues to battle with Amazon Web Services and Google in the public cloud space. Microsoft Azure now owns 10 percent of the market for public cloud and hosted private cloud infrastructure, according to Synergy Research.