The 80s were the absolute worst.
While I'm most likely going to listen to something from the 2000s at any given time, I decided to throw my vote for the 1970s in honor of when music took the quantum leap to becoming great. Genesis, Yes, King Crimson, Pink Floyd, Jethro Tull, Van der Graaf Generator, Rush, Mahavishnu Orchestra, and many many others really changed everything.
Some amazing jazz in the 60s though.