How old do you think your child should be before they can watch movies like:

Teenage mutant ninja turtles?
Star Wars (original trilogy)
Star Wars (I II and III)
The narnia movies?
Tron Legacy?
The hobbit/LoTR?
The matrix?
AVatar?

How do you decide?
All of my kids have seen all the Star Wars Movies. From a young age too.
They have also watched Avatar repeatedly.
They've all seen Tron Legacy
Lachlan is currently very interested in Harry Potter and is recording them off the TV when they've been on just lately
Teenage Mutant Ninja Turtles was on last night, but it didn't hold the interest of my younger two. My oldest wasn't home.
They've seen all Star Trek Movies. With my 12 yr old coming with us earlier in the year to see the latest one at the cinema.
My oldest has seen The Matrix, but doesn't hold the interest of the younger two.
They've never seen LOTR/Hobbit. I watched 9 hours of LOTR in one sitting and found it as boring as bat **** LOL.

We don't decide as such. If we're watching it they can join in and sit with us or do their own thing, and most of your list we have on DVD so they can watch them when they want. We don't watch anything based on horror.