What is your favorite year in the 80s and why?

[Klobmentum Mutilated Herself]

86.
 
Easy contender for best metal year of all time. Thrash peaked with magnum opuses from 3 of the Big 4 + Flotsam and Kreator, while death, doom, and prog metal were all getting started thanks to Possessed, Candlemass and Saint Vitus, and Voivod, with some legacy bands like Iron Maiden, Mercyful Fate, and Motörhead continuing to shine. Master of Puppets, Peace Sells, Doomsday for the Deceiver, Somewhere in Time, Reign in Blood, Rrröööaaarrr, Fatal Portrait, Epicus Doomicus Metallicus, Orgasmatron, Pleasure to Kill, Game Over. It's hard to think of a better year for metal. Just a crazy amount of amazing and influential music.

For mainstream music, you could not avoid my favorite band of all time, Genesis. If you managed to go one day without hearing a Genesis song on the radio or MTV, you'd certainly hear something from Peter Gabriel, Mike + The Mechanics, GTR with Steve Hackett and Steve Howe, or a holdover from Phil Collins's 1985 megahit. It may not have been remotely prog, but a prog ruled the entire music world for a few months in 86, which nobody could've saw coming a decade earlier. 

Jose Canseco, Barry Bonds, and Barry Larkin had their rookie seasons, ushering in the era of baseball I grew up watching.