Holy crap this is going to take a while. But here goes.
edit
To keep this from being a debate on what is metal and what is not I will only use bands listed on metal-archives.com and in my CD collection.
1970 Deep Purple-In Rock
1971 Black Sabbath-Master Of Reality
1972 Deep Purple-Machine Head
1973 Black Sabbath-Sabbath Bloody Sabbath
1974 Deep Purple-Burn
1975 Black Sabbath-Sabotage
1976 Rainbow-Rising
1977 Rush-A Farewell To Kings
1978 Judas Priest-Stained Class
1979 Scorpions-Lovedrive
Favorite album of the 70s Rainbow-Rising
There were some tough decisions on a couple years. 1976 was the biggest debate, Judas Priest-sad wings of destiny, Rush-2112 and Rainbow-Rising, any of those could have been chosen and would all be listed in my top 100 albums of all time.
edit 80s
1980 Black Sabbath-Heaven and Hell
1981 Iron Maiden-Killers
1982 Judas Priest-Screaming For Vengance
1983 Dio-Holy Diver
1984 Iron Maiden-Powerslave
1985 Fates Warning-The Spectre Within
1986 Metallica-Master of Puppets
1987 Savatage-Hall Of The Mountain King
1988 Queensryche-Operation: Mindcrime
1989 Metal Church-Blessing In Disguise
Favorite Album of the 80s Queensryche-Operation: Mindcrime
This was a very tough decade to choose favorites from, a lot of great memories from my high school days. An amazing decade to be young.
edit 90s
1990 Judas Priest-Painkiller
1991 Overkill-Horrorscope
1992 Megadeth-Countdown To Extinction
1993 Savatage-Edge Of Thorns
1994 Testament-Low
1995 Blind Guardian-Imaginations From The Other Side
1996 Morgana Lefay-Maleficium
1997 Bruce Dickinson-Accident Of Birth
1998 Iced Earth-Something Wicked This Way Comes
1999 Nevermore-Dreaming Neon Black
Favorite Album of the 90s Blind Guardian-Imaginations From The Other Side
Ok, this is nearly impossible. So many amazing albums coming up in the 00s. I know I am overthinking like normal. Oh well, like I always say, Sleep is overrated.
Edit 00s
2000 Angel Dust-Enlighten The Darkness
2001 Soilwork-The Preditor's Portrait
2002 Blind Guardian-A Night At The Opera
2003 Dead Soul Tribe-A Murder Of Crows
2004 Ayreon-The Human Equation
2005 Nevermore-This Godless Endeavor
2006 Communic - Waves of Visual Decay
2007 Helloween-Gambling With The Devil
2008 Sylosis-Conclusion of an Age
2009 Centaurus-A-Side Effects Expected
2010 Jon Oliva's Pain-Festival
My favorite of 00s is Centaurus-A - Side Effects Expected, but it could easily be any of the bands depending on my mood.
The 00s where impossible. I probably could have picked any of 10 different albums for each year and would have been happy with them. What a decade for metal.