Best Metallica Album Debate.

In the wake of the big Metallica concert in Lubbock, I've decided to start a fight. What is the best Metallica album of all time. For me, it's definitely one of the first 4 albums. That's about as far as most people (including myself) can narrow it down. You have Kill Em All, Ride the Lightening, Master of Puppets, and And Justice For All. Of those four, I just can't decide which is my favorite. I LOVE Justice and every song is a banger, but Cliff wasn't in that album and Cliff is in my opinion one of the top 5 bassists of all time. Master is a masterpiece but then again, so is Ride the Lightening. Kill Em All is one of the greatest metal albums of all time but Metallica hadn't quite nailed down their signature sound in my opinion. I can't decide. Someone help me settle this once and for all.