Kill em All was the best. Each album after that was worse then the one before it.
Not that Ride and Master are bad, but Master isn't as good as Ride, and Ride isn't as good as Kill em All. ...And Justice For All was ok, but the last decent album they made.
IMO, Metallica has made only one sub-par album. That was Justice. The mix on that is awful.
I personally prefer the black album. But of the options given, I go with Lightning. that was the first one I ever bought, so it kinda shaped my early opinion of them.