For me it's the 80's because it's simply boring. All those crappy outdated programmed drums and synths and boring arrangements, plus in order to make songs more futuristic and modern, producers lost all the organic touch that earlier music had.(plus the abolition of vinyl and introduction of digital technology)
Best music for me was in the 70's because it had all the old flavor from earlier decades(jazz, soul, funk) combined with inovations(progressive rock, jazz fusion, electronic) that were exploited much more in later decades.
90's is all about Hip Hop and Rage against the machine. And prodigy.