I saw Cars 2 over the weekend. My son pulled my arm to get me up out of the seat and then lead me out of the theater...for what it's worth. And this is a kid who, the first time he saw Cars, watched it from start to finish (on DVD).
For me, I didn't think it was as good as the previous film. It's okay, but the story is somewhat involved and a bit too complex for most kids under, say 5-6 years old.
It seemed pretty rushed, too...a lot happening and squeezed into the 100+ minutes of the film. That, and the characters don't really connect like they did in the first installment.
It's worth seeing...just don't expect to be as good as Cars. I'd give it 2 1/2 out of 4.
I also saw Super 8 recently. Let's just say we're talking the usual Spielberg story elements, not in a bad way, just the way it's constructed, i.e. the kids in the story are the center of things, not the alien or special effects. Nice story and lots of fun, though I thought it got a bit too carried away for the last 30-45 minutes. Definitely worth seeing.
3 out of 4.