Take Transformers, for instance. to me, there was a clear line delineating Autobot and Decepticon, good and evil. My mom saw 30 foot metal monsters, live, in her living room. Needless to say, I skipped ROTF and DOTM with them. Iron Man was borderline, I think Mom may not have always quite gotten that there was a man in the suit
On the other hand, Captain America: the First Avenger, was excellent for my Progenitors. it held their attention, they felt for the characters, there was nothing in there to offend them overly. This is in spite of the fact that my father fought in WWII, or maybe even because of it.
My mom has three criteria for a good movie: Singing, Dancing, and a Happy Ending
Technically Sweeney Todd: The Demon Barber of Fleet Street and Cannibal! the Musical fit that, and I would never show those to my parents