Somewhat, there is some limitations/hacks that have to be done.
I had read that esxi running virtual esxi is possible but not supported
If you are running hyper-v (server or role) you will run into issues with networking and are limited to 32-bit guests as hyper-v will not pass along the visualization bits to the esxi vm guests.
Also you will have to customize the esxi iso to add the virtual nic drivers that hyper-v uses as they are not included any more in 5.5 or newer (can use 5.1 drivers)
I would not try this on your production server until you know what limitations/gotchas there are