I like The Black Album
As for Metallica selling out, they probably wanted to try something else. The Black Album shows versatility, they got to experiment with other ways of working in the studio (less overdubbing), they nailed the new sound they were going for ..
Expecting a band or an artist to do the same thing over and over again is selfish from a consumer point of view. I mean, if you like Metallica, how about giving them an ounce of freedom in their artistic pursuits? I'm sure they like to try different things and if they also consider music a job (which it is to them) in which they want to make more money, isn't that also fair? The Black Album features songs written by members of Metallica, so it's still
them.