When I go to deploy the 9.1 OVA on a standalone 6.5.0d ESXi host (5310538), it gives me an error about compressed vmdk images in the ova:

The VM you are trying to deploy contains compressed disk images. Host Client
 is currently not able to deploy VMs that contain compressed disk images.
 Please consider using OVFTool or vCenter Server to deploy this VM.

That sounds like something I could fix, but ultimately other problems come up and the host client OVA importer cannot deploy the vsim ova.  In older versions I would fall back to the thick client, but there is another way: ovftool

ovftool is included in VMware Fusion and VMware Workstation, or you can download a standalone version from VMware. 

The basic syntax to deploy the Simulator on a standalone ESX host is:

ovftool --datastore=<datastore> vsim-esx-DOT9.1-cm.ova vi://<user>:*@<host ip>

This assumes you have VMware port groups named "Cluster Network" and "VM Network" already created, and will produce a thick provisioned VM named "vsim-esx-DOT9.1-cm". 

Here is a more complete example if thats not what you need:

ovftool 
    --datastore=<datastore> 
    --diskMode=thin 
    --net:"Cluster Network"="<cluster network name>"
    --net:"VM Network"="<data network name>" 
    --name=<vm name> 
    vsim-esx-DOT9.1-cm.ova 
    vi://<user>:*@<host ip>

It will prompt for the password as it deploys, which should look something like this when it succeeds:

Opening OVA source: /Users/Me/Downloads/vsim-esx-DOT9.1-cm.ova
The manifest validates
Enter login information for target vi://10.10.10.40/
Username: root
Password: *********
Opening VI target: vi://root@10.10.10.40:443/
Deploying to VI: vi://root@10.10.10.40:443/
Transfer Completed                    
Completed successfully

Now you can log into the host UI, power it on, open the console, and complete the initial setup.