I really liked "The Black Album" when it was released. I just got bored of the music fairly quickly. It's like the opposite of Opeth. With Opeth I usually like a new album right away, but it grows on me with every listen and then I really start to love it and keep coming back to listen to it after years and years.
I still listen to the old Metallica albums from time to time, but every time I turn on "The Black Album"... I don't know... I kinda get bored and turn on something else. I'm not saying it's a bad album though, just not as interesting as the old ones.
As for disliking others starting to like a band that 'belonged' to me. I can't relate to that. I've actually tried to get many people I know to keep an open mind and listen to some of the music I like, hoping that they'll enjoy it.
I actually have a little story from those days... There were a couple of girls that from time to time used to ride in my car back then, around the time "The Black Album" was released. I had made a mixed tape to play in the car. One of the songs was Metallica's "One". Every time that song came on, they were both like "Turn off that awful music! It sounds horrible.". After a couple of weeks, when "The Black Album" was released, and all their friends had started to listen to it, they asked me to make a copy of it for them on tape.
I was happy to do so, and I also added "One" to the tape, since there was room for a few extra songs. A few days after that, they came to me and said:
"Damn! The album is great and the song One is really really good!".
So I said "Umm... That's the song you've kept telling me you hated and asked me to turn off every time you heard it in the car."
Both of them said "No! That's not the song. One is really good. It was some other song we didn't like."
I played the mixed tape again and they were both like "No. That's not the song we hated. This is a good song."
That part of it annoyed the crap out of me. Not that they started to like Metallica. That was fine by me. It's the part that they couldn't accept that they were so close minded and used to hate them before when I was trying to show them that they're actually good. And that what actually made them start listening to Metallica was pure peer pressure from their female friends at school that had started to listen to them.