I prefer the proven technology of the D5100 to the new and unproven technology of the D3200. The D3200 is an entry-level camera with high resolution. There is absolutely no way whatsoever I would limit myself to one prime focus lens. That is just too restrictive. An 18-55 is to restrictive in my opinion and would not be my first choice. Personally I would only choose anything in the choices you provided if I had no choice. They are good equipment but not what I would pick. Based on the choices provided, the D5100 and 18-55 were, in my opinion, the best compromises.
D5100 with 18-55mm. It's the most versatile of your choices. The D3200's 24.2MP sensor has a higher pixel density than the D800, right? So I think this camera is more unforgiving for handheld shots and you have to deal with bigger RAW file size.
I just kept looking at this thread, pondering the question and thinking "Wait, WHAT??" I'm too much of a literalist to answer the question the way it is posed. This is why I have trouble filling out simple forms. First of all--NO WAY are the D3200 and D5100 going to be the last two cameras left on earth, no matter what sort of disaster has overtaken us to destroy the other 632,946 types of cameras. Ditto for those particular lenses. Even if I could accept that basic premise, which I can't: as another poster mentioned: WHY have the other cameras been destroyed? This is important information to have before deciding which of the remaining camera/lens options might be the best choice. Also--are the computers all okay? Because I can't imagine all the other cameras being destroyed and not the computers. And with no computer to either view or process the photos, a digital camera is kinda pointless. Additionally: For all those cameras to be destroyed, I can only presume that some cataclysmic disaster has occurred and it seems like my money would be better spent on guns and ammo, or seeds for a vegetable garden, than on a camera. Are all the people still here? Is there going to be anyone here to ENJOY my photos, or am I just going to be entertaining myself with them? What about TPF? Is it gone? If so, who is going to adequately C&C my photos with whichever camera I pick? I could, almost literally, go on ALL DAY with my questions about this. Suffice it to say, I cannot fill out this form. Now, if you're just asking which of those options we think is a better all-around choice: the D5100 and the 18-55 lens.
Pffft a 5100 with 18-55, and a whole can of whup a$$! More than likely the electricity with be on for while so grab like 20 PC's, 3 generators and lots of photog books.