That's what I like about opinions. I'd take LOTR over MM every day and twice on Sundays! Much better software and less repetition. As far as the licensed pins not being worth as much as originals, just look at TZ, TAF, MB, IJ, SS, SM, Creech, etc. Most of the big money titles are licensed.
I can understand your reservation if you are concerned about future values. MM is almost a sure bet that it will continue to rise in value, whereas LOTR and Avatar LE are more of a risk if you are worried about holding/rising values. Personally if it were me I'd trade away the MM for those titles, but then again I don't really like the game that much. It really comes down to how much you like MM. If it's one of your favorite games and you play it all the time, by all means keep it! If you are getting tired of it and you would rather have some new games to play, then trade it away!