The Lion King had a major character's father being murdered onscreen, another major character being eaten alive by hyenas, and a young child snuggling up beside the corpse of the above-mentioned recently deceased father. Tarzan opened with a blood-stained cabin containing two corpses and an infant being eaten alive off screen, and it ended with the onscreen shooting death of a major character and the hanging of the lead villain. The Hunchback of Notre Dame had an onscreen neck-breaking murder of a young mother, the attempted drowning of her baby, and an entire subplot involving the villain's desire to screw and/or murder the heroine because of his guilt-ridden lustings for her that felt like a cross between Schindler's List and Sweeney Todd (great movie and great song though... why don't they make kids toys that sing "Hellfire"?). Yet they all received G-ratings from the MPAA back in the 1990s. Yet just last week, Walt Disney's Tangled received a PG rating for the unholy crime of 'brief mild violence' (trailer 01 and trailer 02).
Back in my day (about ten years ago), the PG rating was a kiss of death for an animated feature. The Black Cauldron in 1985 was the only major Disney cartoon to receive said rating, and it was an infamous flop for the struggling studio that instigated the changing of the guard which brought about the Jeff Katzenberg/Mike Eisner/Roy Disney 1986-1994 era-of-awesome (I'd argue that it lasted until 1999, but I'm a fan of their post-Lion King work). As the 90s drew to a close and Dreamworks waged a genuine campaign against the Disney animation monopoly, they used the PG rating to signal that their initial films (Antz, Prince of Egypt, etc) would be a bit more hard-edged than the stereotypical all-ages Disney films. Fox tried their luck with the PG-rated Titan A.E. in summer 2000 and flopped so hard ($75 million budget > $36 million worldwide gross) that Fox nearly ceased to even have an animation branch, and the one-time would-be Disney rival Don Bluth ceased to have a career all-together. While Disney tried their hand at hard-PG action in 2001 with Atlantis: The Lost Empire (if you want a film that feels like it inspired Avatar just as much as The Battle For Terra...), but the film grossed just $84 million domestic.
Ironically, just a month prior, Dreamworks would release the film that would more or less completely kill the notion that PG = box office death. Of course, we're talking about Shrek, which received a PG for 'mild language and some crude humor'. The film established Dreamworks as an equal to the Disney animation empire, grossed $262 million in the US, and won the first-ever Academy Award for Best Animated Film. Once Dreamworks proved that PG didn't necessarily equal box-office doom, the floodgates opened. In fact, of their twenty animated features, only three Dreamworks cartoons have been rated G (Spirit: Stallion of the Cimarron, Wallace and Gromit: The Curse of the Were-Rabbit, and Chicken Run). All three Ice Age films from Fox (the franchise that revitalized Fox's animation department) all had PG ratings, as did Robots (Horton Hears A Who, a $145 million-domestic grosser, had a G).
The weird side-effect of this over the last decade is that while more and more animated movies have been willing to go with the PG rating, it has seemed harder and harder to actually get a G for films that seemingly would deserve it. Sure, the two Pixar PG-films (The Incredibles and Up) had onscreen deaths and heart-wrenching drama, but Lilo and Stitch basically got a PG for having a rude and obnoxious alien furball as a main character (or, um... 'mild sci-fi action'). Most Pixar films, even the emotionally-devastating Toy Story 3, went out with G ratings, but Bolt went out with a PG for basically having a (fantastic) curtain-raiser opening action sequence that was quickly revealed to be fake and for a climactic moment of fiery peril for the lead characters.
Point being, back in my day, you had to EARN a PG rating for your cartoon. You had to have Earth being blown up in the opening scenes (Titan A.E.), you had to have corpses coming back to life and attacking our heroes (The Black Cauldron), you had to have a ten-year old child killing enemy henchmen (The Incredibles), you had to have a 200-person expedition team getting wiped out by robotic monsters (Atlantis: The Lost Empire). You at least had to have some token vulgarity and the occasional profanity (the Shrek series). But now that the PG rating is no longer considered kryptonite, and the G rating can be considered as 'uncool' for animated films as it generally is for live-action films, studios don't seem to be even putting up a fight before taking that PG for something as meaningless as 'brief mild violence'. It makes one wonder whether the Disney cartoons of my youth, such as The Hunchback of Notre Dame, would be PG-13 by today's standards. Heck, maybe it would get an R.