If I walk thorough the New Virtual Machine Assistant in VMware Fusion 6.x, under Microsoft Windows, Windows 2000 Professional, Windows 2000 Server and Windows 2000 Advanced Server are still listed and a Virtual Machine of them can be created. Now while they may no longer be officially supported (and really, why should they since even Microsoft doesn't support them anymore!) nonetheless you can install them.
BTW I have a Windows 2000 Server Virtual Machine that runs fine under VMware Fusion 6.x.