I have played several of the Lego Wii games with my son, and like them all. But, the Lord of the Rings surpasses all of these in both graphics and breadth of play.
There is terrific opportunity for exploration, and to work on team play and problem solving. I do wish the puzzles were a bit more mentally taxing, rather than smash everything until you find what you need, but still great fun.
When it comes to playing with kids, I think my 9 year old son is right in the sweet spot age for the game - even a bit younger would be OK as long as there's some discussion about the fighting. They also temper some of the more gruesome scenes in the movie so as not to be too much for kids.
For example, in the movie where Boromir is killed by multiple arrows from the Uruk-Hai and Aragorn very gruesomely fights and kills the attacker is way too strong for my son right now.
But, in the game, while Boromir is still shot several times they lightened it up by having the Uruk-Hai shoot him first with an arrow, then some silly things like a banana and almost a live chicken.
My son is a plow-right-through sort of player, so I personally am looking forward to going back into free play mode and finding all of the many things we missed on the first run.