Physical server transited to virtual server infrastructure (VSI) and desktop device to virtual desktop infrastructure (VDI) have the crucial problems of server consolidation, virtualization performance, virtual machine density, total cost of ownership (TCO), and return on investments (ROI). Besides, how to appropriately choose hypervisor for the desired server/desktop virtualization is really challenging, because a trade-off between virtualization performance and cost is a hard decision to make in the cloud. This paper introduces five hypervisors to establish the virtual environment and then gives a careful assessment based on C/P ratio that is derived from composite index, consolidation ratio, virtual machine density, TCO, and ROI. As a result, even though ESX server obtains the highest ROI and lowest TCO in server virtualization and Hyper-V R2 gains the best performance of virtual machine management; both of them however cost too much. Instead the best choice is Proxmox Virtual Environment (Proxmox VE) because it not only saves the initial investment a lot to own a virtual server/desktop infrastructure, but also obtains the lowest C/P ratio.