interoperability with the leading public clouds (AWS, GCE, Azure)
cost and support
Operating System. Sometimes the O/S can be vitally important. I've learned that lesson the hardway.
ROI and Security.
Resilience, global footprint, low latency, a platform and tools to integrate with on-premises systems.
Performance, capacity and capabilities
Security, and yes, ROI too.
ROI and variety of instance types
"Criteria" is plural, so I'll say reliability and security.
Obvisously I'll say ROI. Assuming going to the cloud will raise availability and lower cost.
To Go Green Computing while researching on Iaas
Redundancy and WAN costs