Two

Simple story... why say more? It nails it's premise. World War 3 kills all or most of the human race and we're viewing 2 of the survivors. The message is that the 2 warring sides should not have been at odds in the first place. Distilled down to representatives from each side, we see they have everything to come together for:

Security... Finding resources... food, shelter, etc... Survival... Love...

At the end they've decided to pool their resources, (she finally does), so they will survive. Simple story, expressed in the limited budget of the early 60s television landscape. We see it in 2009 as somewhat old and maybe predictable. In the early 60s, no one had seen such stuff... I give it a 10...