Definitive Half Decades

I don't contribute to many discussion boards. Just don't have the time for all the give and take that is required. But I occasionally do, and this one at poptimists Design of A Half Decade caught my eye. The songs that defined a half decade. Click on the link and you'll get the idea. I have no problem with most of these and suggested "Lovesick Blues" for 45-49. The UK only 70-74 goes over my head, so I was thinking for that half decade maybe "American Pie" or "What's Going On", something like that sounds definitive.