Has anyone tried if Windows Server 2003 works on ESXi 6.5?
This is not really a question for this forum.
However, you can usually find the answer to this sort of question in this document
According to this document, Windows Server 2003 is a supported guest OS on vSphere 6.5
Discussion moved from VMware Hands-on Labs to Virtual Machine, Guest OS and VM Tools
Yes, Windows Server 2003 works on ESXi 6.5.