Because everyone else is doing this, I might as well take part.
Metallica:
Master of Puppets
Ride the Lightning
...And Justice for All
Kill 'em All
Death Magnetic
Black album
St. Anger
I've not listened to Load or Reload, so I cannot rank them. However, from what I've heard on those albums, I'd put them just above St. Anger.
Megadeth:
So Far, So Good...So What!
Rust in Peace
Peace Sells...But Who's Buying?
Killing is My Business...And Business is Good!
Countdown to Extinction
Youthanasia
Cryptic Writings
The System Has Failed
United Abominations
The World Needs a Hero
Risk
DragonForce:
Valley of the Damned
Sonic Firestorm -- Inhuman Rampage
Ultra Beatdown
And since people are throwing in other bands as well, I'll throw in Iron Maiden and Helloween in my post.
Helloween:
Keeper of the Seven Keys Part 1
Keeper of the Seven Keys Part 2
Helloween/Walls of Jericho
Keeper of the Seven Keys Part - The Legacy
Better Than Raw
Master of the Rings
The Dark Ride
Gambling With the Devil
Rabbit Don't Come Easy
The Time of the Oath
Chameleon
Pink Bubbles Go Ape
Iron Maiden:
The Number of the Beast
Iron Maiden
Piece of Mind
Powerslave
Somewhere in Time
Seventh Son of a Seventh Son
Brave New World
Killers
A Matter of Life and Death
Dance of Death
The X Factor
Fear of the Dark
No Prayer for the Dying
Virtual XI
Hopefully I don't get tempted to do more of these albums rankings.