I'd have to say that everyone saying Cars 2, Toy Story 3, Beauty and the Beast, Lion King, etc should be PG are just being a little too oversensitive as far as content. G means "General Audiences" - it generally is acceptable for most people to watch it.
More importantly, PG means "parental guidance" - you guys think cartoon violence is enough to warrant parental guidance? Never mind that parental guidance should be a no-brainer with any child watching any sort of media or entertainment.
I'd say more PG movies should be G than more G movies need to be PG. Frozen was a G rated movie if Monsters University was. Despicable Me has nothing inappropriate that I can think of. The new Muppet movies had fart shoes... that's it. Tangled had a couple drips of blood - you see more at a kids soccer game than the movie showed. Pretty much any PG movie with "rude humor" or "mild thematic elements" is a G.
Rango, Coraline, ParaNorman and HTTYD 1 and 2 are the only PG kids movies I can think of that actually warranted the PG rating. Secret of Nimh and Black Cauldron too. Watership Down as well. The first two Shreks and Antz were pretty racy for family movies, too - but they shouldn't be PG-13 just because they have intense moments or profanity or sexual innuendos.
When did PG become "kid movie that's okay for anyone to watch"? And don't get me started on people saying the Indiana Jones movies and Ghostbusters should be rated R. PG-13, sure. But R? Next to today's R rated films, no. They're way too light-hearted and squeaky clean (as far as realism/effects go) to be R rated. Goonies, Big, Beetlejuice all probably should have been PG-13 in hindsight. Back to the Future can stay a hard PG since there's no drug references or F bombs. I'd even say both Ghostbusters movies could probably remain PG (some language and a little action, but that's it).
Very few kids movies are intense enough where a PG is legtimately warranted. And for the "what about preschoolers?" argument... well why are they watching many movies to begin with? I'd say you need to be about 5 before you should regularly watch movies that feature sad/tense moments. Even then, it depends on the kid. Coraline shouldn't be shown to anyone under the age of 7. Common sense. Rango might fly over the head of a 9 year old. Common sense. But that doesn't make them PG-13 in the same way Titanic, Men in Black or The Avengers are PG-13.
And if you sincerely think Cars 2 should be PG because "the cars are portrayed as alive just like humans"... I don't know man
Kids don't need to be sheltered because Mom and Dad think some intensity, maybe some cuss words, or even an adult joke makes it a hard PG-13. Or that something resembling conflict makes Toy Story 3 a solid PG (it's borderline G - a cuss word or the characters dying in the incinerator probably would have gotten it a PG. Personally, I think most kids over the age of 4 can handle Toy Story 3 just fine with a G rating)
I'll agree that Raiders of the Lost Ark and Airplane! are automatic PG-13s now. I'll agree that the original Planet of the Apes should have been rated PG from the start. But when something as innocent as The Wizard of Oz gets re-rated PG for "some scary moments" (aka the Wicked Witch and the flying monkeys' 5-10 minutes of screen time) or the Muppets "for mild rude humor" (fart shoes!!

so inappropriate! I can't believe Disney put such a thing in a family movie! This could never pass for G!)
Rant done lol