Kill 'em all is the best one by a mile for me, they never regained that sheer energy in any of the other albums, in fact it diminished with each album that came out. Then would be Ride the lightning, some classic tracks on there. Master of puppets is ok I guess but imo the albums get progressively worse in sequence, with only the first 4 being any good.
I'd even say 'No Life Till Leather' but that would be pushing it. and as long as we're in a gay metallica thread, let me be a tad bit gayer for a flash and just say Mustaine > Hammet. He just plays it better.