SQL Server 2008 Cluster Across Two VMWARE Hosts
As said in the comments, I can (almost) conclusively confirm that you will require shared raw LUNs with RDM, when you want to cluster 2 x virtual (vmware) SQL Server nodes that are on different hosts, instead of using VMFS.  

The VMWare documentation also explicitly mentions the use of unformatted LUNs

*I guess (and I have never done touched on it before) the only possible exception that spring to mind may be in you use SQL Server 2012 AlwaysOn on SSDs. Oh, and possibly iSCSI, which is as you said, not an option. *