I had a need to apply a Group Policy only to VMware virtual machines. One possible option was to filter on the vendor of the network adapter, which can be determined by looking at the MAC address. The public listing of company ID assignments can be found at IEEE OUI Public Listing and is updated daily. At the time of this writing, VMware has 00-05-69, 00-0C-29, 00-1C-14, and 00-50-65 as their company ID assignments.
This WMI filter should then pickup VMware Virtual Machines:
SELECT * FROM Win32_NetworkAdapter WHERE MACAddress LIKE "00:05:69%" or MACAddress LIKE "00:0C:29%" or MACAddress LIKE "00:50:65%"
Other Virtualization Vendors
Virtual Box: 08-00-27