Microsoft Hyper-V Microsoft introduced its hypervisor in 2008, and has continued to release new versions along with the new Windows servers. Hyper -V helps one expand or establish a private cloud environment, promotes effective hardware utilization, improves business…

KVM is Hypervisor and vSphere is platform but Ovirt is platform with KVM. The big difference it's cost but vMware is leader on Virtualization.

I haven't personally worked with NComputing. But I think VMware Horizon View is a better, because VMware is a leader on virtualization in the world and you see support , development and applications...