1987 was a decent year for metal, thrash metal was thriving at that point, heavy metal also was, but this also saw the beginning of death metal.

Here is my ranking:

1. Savatage - Hall Of The Mountain King
2. King Diamond - Abigail
3. Testament - The Legacy
4. Death Angel - The Ultra-Violence
5. Helloween - Keeper Of The Seven Keys Part I
6. Sanctuary - Refuge Denied
7. Def Leppard - Hysteria
8. Bathory - Under The Sign Of The Black Mark
9. Death - Scream Bloody Gore
10. Candlemass - Nightfall
11. Whitesnake - Whitesnake
12. Guns N' Roses - Appetite For Destruction
13. Sodom - Persecution Mania
14. Anthrax - Among The Living
15. Running Wild - Under Jolly Roger

Another good year in metal, probably even very good, a couple of relevant albums were released in 1987, but not tons. Compared to the years surrounding it, this year was a bit subpar. But hell, subpar in an end-of-80s comparison for metal is still a great result.
I have:

1. Death Angel - The Ultra-Violence
2. Helloween - Keeper Of The Seven Keys Part I
3. Savatage - Hall Of The Mountain King
4. Anthrax - Among The Living
5. Testament - The Legacy
6. Sepultura - Schizophrenia
7. Dark Quarterer - Dark Quarterer
8. Sodom - Persecution Mania
9. Candlemass - Nightfall
10. King Diamond - Abigail
11. Necrodeath - Into The Macabre
12. Assassin - The Upcoming Terror
13. Dead Brain Cells - Dead Brain Cells
14. Holy Terror - Terror And Submission