Remember that scene in Back to the Future II where Doc explains the time paradox? Biff used the almanac to change his own destiny, and create an alternate reality, referred to as 1985a. He only made one small change in 1955, but the consequences of that change sent shock waves across Hill Valley for the next 30 years.
Suppose we revisit the rock n roll time line and make one slightly different pick in the 1950's. What effect would that have on all future song selections?
Perhaps the reason it was so difficult for me to select a rock song to represent the 2000's is; rock is no longer the dominant genre, and the best songs being made right now do not feature the electric guitar. After all, rock is not the only valid form of expression.
Over the next few days I would like to draw an alternate musical timeline for you. A list of the most significant hip hop songs from each decade. Ready? Okay. We'd better back up or we'll never get this thing up to 88 miles per hour.