The best replacement for xenserver is vmware.

The best alternatives to xenserver are rated as following:
★★★★★  vmware
★★★★★  esxi
★★★  xen
★★★  vsphere
★★  hyper-v
★★  kvm
★★  xendesktop
★★  proxmox
★  xcp
★  esx
★  xen project
★  ovirt
★  hyper v
★  xenapp
  esxi 4.1
  vmware server
  xen hypervisor
  vmware esxi

Your alternative for xenserver is not listed? Suggest!
Speaking about xenserver, one probably shouldn't forget about openfiler.

Other search terms related to xenserver and their ratings are:
★★★★★ openfiler
★★★ xendesktop
★★ netapp
You have in mind a companion for xenserver and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of xenserver in all years. Click on graph for more.
xenserver
vmware
esxi