Is this a standalone ESXi server, so presumably has local storage and no vcenter. If so then I would shut the vm down unregister it from the host and copy and paste the full virtualmachine folder from the datastore to the new one.
You could also save some time by using the free veeam backup and recovery product to zip the vm and then extract it to the new datastore. http://www.veeam.com/virtual-machine-backup-solution-free.html
You could also use vmware convertor essentially v2v the vm from one datastore to another. http://www.vmware.com/products/converter/overview.html