Great discussion....
GnR- Appetite then death by power ballad...just tragic
Metallica- Great until the Black album but totally sold out. That is when they died musically....they need to listen to the lyrics of Whiplash......go all the way back to their roots.
AC/DC- wish I could unhear Fly on the Wall but all the other albums are pretty much solid....death by just old age.....they never really changed....you can recognize their new songs just as quick as the old. Very few bands stick to doing what they do well.
Many bands change over time and not for the better. And somewhere during those changes the bands should probably have died.....examples are the Beatles. Listen to their early stuff and then their later stuff....completely different. Metallica is another example.
And some of these bands that find a way to keep touring need to just hang it up...Lynyrd Skynyrd needs to let go.