Try to keep from flamewars, here, since even things mentioned might still have some value, at least historically. For instance, Springsteen has some good stuff, despite me not liking all the horn tracks.
My vote for worst-aged genre is the fairly recent genre of nu-metal rapcore. I don't see that coming back anytime soon (or ever), what with its (IMO) very inauthentic "rage" and chaotic, unmusical bands, for the most part. IMO, only two rock bands successfully incorporated rap - Rage Against the Machine and Red Hot Chili Peppers (to a degree he raps, anyway) - and neither of them could be considered nu-metal or really rapcore. Bands that personified that genre are generally derided, such as Limp Bizkit.