Heading into my favorite era of music. Top 5 are stone cold classics. I also think this is the best year for thrash (as evidenced by Flotsam and Jetsam, Metallica, Holy Terror and Razor being left *off*).
Jane's Addiction - Nothing's Shocking (a blatant 5, you should check it out if you like alt.rock)
L7 - L7
Ministry - The Land of Rape and Honey
R.E.M. - Green
Soundgarden - Ultramega OK
I enjoy Nothing's Shocking as well as those Ministry and Soundgarden albums, but they didn't quite make it. This is really when my collections per year start increasing in size. It goes from 30 in 1986 to 41 in 1987 to 49 for this year.