I downloaded ISO images for both CentOS 6.6 Minimal and DVD (Full).
I installed both images into VMs under esxi 5.5 without difficulty.
When I tried to install on physical HW, the Minimal install works fine, but the Full install fails while booting the DVD image and just reboots the host in an endless loop.

Since im trying to get to a "Desktop" configuration, I was hoping the Full DVD image would work, but since it's not working on my HW (HP DL980 G5), I went ahead and installed the Minimal install.

Then I ran the group install for Desktop and "Desktop Platform", and rebooted into runlevel 5.

The console does not display correctly, and I am also not able to RDP into the box without an error being displayed.

I can get some screenshots if that will help explain the issue, just let me know if they are needed.

1) Why am I not able to install Desktop onto physical HW when the same ISO works fine on a VM?
2) Why am I unsuccessful in setting up graphical login on top of a minimal install? Where can I find the required steps (Perhaps I missed something important)?

Because of different hardware and software(BIOS/UEFI and others) in VM and your real machine.

Great, but how do I resolve? The Minimal install works fine, but the Desktop install won't even get to the DVD setup screen...

There may be an incompatible kernel driver that crashes during the hardware install. There may be a kernel parameter you can pass to prevent the install from rebooting and to allow you to catch the error when it occurs. Unfortunately I don't know what it is but Google should have the answer if you search for kernel grub parameters.

You could check dmesg to see what hardware you have on the physical machine.
Try to see what card you have.

Got it working. I installed minimal edition, then added desktop after it completed. Runs fine this way.