Ummm, it's tempting to say that ANY TIME you have characters who are intrinsically evil (i.e., monsters of any kind) -- as opposed to people who are evil by choice -- then you're talking about cheesy Hollywood stuff or one-dimensional kid's stuff. I wouldn't offer that as a hard & fast rule -- Dracula isn't really kid's stuff and it's not cheesy, yet he's a monster -- but it's a good guideline and, in the case of LoTR, I think it holds up.
Mark W.
Now I'm positive you haven't read it. The main theme throughout the trilogy is the protagonist's struggle with the seduction of power and it's corrupting influence on the soul.
Might be a good idea to read it before you trash it.