Rock Music: 1951-1976 vs. 1977-2003

There have been a number of posts recently where people have voiced opinions about how much better music was back when "Star Trek" was in it's original run. This is a post intended to examine the issue in a little more detail.

Let's say rock & roll started in 1951 with "Rocket 88" and has evolved continously through the present day. That's 52 years of 4/4 music with a heavy backbeat and it puts the midpoint at about 1977, or the start of the punk/new wave sound. My question is which of these two periods produced the best music. Voice your opinion and explain why.