I get into arguments about this very topic all the time ... but you have to remember "which album is better?" is subjective ... but I can sum them up for you ...
Kill em' all - very thrashy, rough sounding but pure unfiltered Metallica its also worthy to note that Dave Mustain played a big role in the creation of most of those songs. (you can tell the influence Motorhead and Diamond head)
Personal fav. Tracks
Hit the Lights
Four Horsemen
Whiplash
Ride the Lightning - Seemed to be a more subtle approach to their music. Still thrash, still fast but filled with more subtle nuances that seemed to invoke feelings of love or distrust as well as common themes of war and pain. A well thought out album Starts out strong and leaves you in mystery ... (Most of the songs have a Distinct sound to them, most riffs sound Jamesish' But the new bassist Cliff Burton adds a whole new level to each song ... The fact that the bass does not only follow the root as with most bands lends to its complexity)
Personal fav. Tracks
Ride the lightning
Trapped under ice
Creeping Death
Master of Puppets - Arguably their most acclaimed album, You finally hear (my opinion) Kirks Style (Formerly of Exodus) integrated into the metal machine known as Metallica. Its Heavy, Thrashy and combines a plethora of melodic styles. (Has all the songs aspiring guitarists tend to learn first ... all I can say is "I love dual harmonies!")
Personal fav. Tracks
Master of Puppets
Disposable Heroes
Orion
…And Justice for All - Also known as the bass-less album. Most tracks (on original release fixed on the remastered release) Lack an audible bass (its there just very faint) ... Most say it was due to Cliff Burtons death, I say Lars and James did the mixing so I blame them... Its a very strong album, more simplistic riffs but very melodically pleasing, retains the heavy sound I loved from the previous albums. Seems to be more of an emphasis on the solos here as its some of Kirks more "fancy work" (prior to the writing of this album Kirk was learning under Joe "Satch" Satriani ... his solos reflect it being more melodic then just fast and utilizing more effects, the wah and the whammy bar)
Personal fav. Tracks
Blackened
The Shortest Straw
Dyers Eve
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I won't even try to hide the fact that the following, no matter how much I try will seem ... Well, with the exception of a few songs I don't like where they went musically ... Personally I think it stems from where they where in their lives to the simple fact that its hard to write something when you haven't really played in years but you have a record company and a contract pushing you to write. Most guitarists will tell you that the rest of the albums seem almost phoned in
they retain none of the "trademark" Metallica riff patterns and the solos are just lacking... Thats why you get a distinct break in fans, Old Metallica (pre-Black album