What is the difference between various VM solutions? I'm new to the Mac platform and need to figure out which virtualization platform is best for me.

Is there a comparison list of features (and missing features) for each of the major virtualization platforms?  (VirtualBox, VMware Fusion, Parallels Desktop, Microsoft VirtualPC, or VMware ESX?

I have a license for each and am running on a retina MacBook Pro with 16 GB of RAM.  I need to run a number of Microsoft operating systems in 64-bit mode.
As you've pointed out, there is plenty of virtualisation software. However, the most famous are Parallels and VMware Fusion (the other ones I haven't used, so I can't give you an opinion about them).

In my opinion, Parallels is the more robust one and gives me the best performance. There are a lot of online battles going one between both camps and there both apps have their (dis)advantages. For me, Parallels is the best way to go, because it has the most functions.

For most people it's a close race and they let the price decide. Both companies often hold special sales, so you should look for those kind of things.