I have installed several other VM on the host. XP, Vista, 7, 8, 8.1 - Same result
Host machine was a fresh install of windows 8 and then a fresh install of VM. and then installed the fresh guest on the host.
Same issue when tried on other 2 computers. So this is not related to just the PC hardware.
I have done hundreds of searches on line and there are people everywhere with this same issue. Dating back to 2003 to 2013 having this very same issue. Some have had lick chnaging setting on the HOST network adapter. I have made the same changes and still no change in speed.