Time warp concert: The Who performing Tommy at the Met in NYC to 15-minute standing ovations. One of the legendary concerts of all time.
If only they hadn't had that last drink/hit concert: Jimi and Led Zeppelin at the Rainbow room in London 1970.
Time Warp 2: Pink Floyd The Wall Live in LA.
If only the people around him could have understood back then: The Beach Boys perform "Smile" for the first time at the Monterey Pop Festival, 1967.
As far as contemporary bands and "dinosaurs" I guess I've seen who I want to see.