I guess my biggest problem with a LOTR park is the story is such an unhappy one for so much of the story. Like 90%+ is trials, death, war, etc. Thats not your typical theme, amusement park fare. I mean a Mordor land would have to be a desolate place. Would that really be the kind of thing that would be popular for families? Hey lets pop over to mordor to grab some burgers for lunch? I can see a shire land and Rivendell probably, but after that, how many lands could you really flesh out from the books that wouldn't be either mood killers or only loosely based on the story? I could see a single large land or a couple similar to how the harry potter deal is, but any more than that and I think you run into trouble making it fun for the general public.
I say this knowing they would never build a whole park dedicated to the tolkein stuff, but if it happened somehow, I'd still go. lol