Batman: Year One is a really good read. You'll probably recognize a few bits from it that they used in Batman Begins. Superman: Secret Origin was okay IMO, but I prefer the John Byrne Man of Steel version.
Absolutely. At no point in Man of Steel do the Legion of Supeheroes show up with expressions on their faces that indicate they want to wear your skin. Also, it puts forward my personal favorite version of Krypton, the sterile, inhuman Krypton, which will probably never return as everyone else but Byrne and me seems to hate the place.
But everyone always forgets about Superman: Birthright, which was the retcon between the two, by Mark Waid and--well, somebody drew it, I assume. Superman's my vegetarian hero.
Batman: Year One is a seminal piece of comics art. David Mazzuchelli is in full force. Frank Miller writes some words, too, but these aren't terribly important.
I'll also cop to liking GL: Secret Origin to a degree. It's the absolute reverse of an ordinary Geoff Johns comic: very little superheroic works correctly (Hal's training is fine, but Atrocitus and Black Hand are shoehorned into the GL mythos very round hole-square peg style, and no one cares about Hector Hammond's best telepathic imitation of Lonely Island's The Creep), yet the human aspects of the story are actually recognizable, and even made me like Hal Jordan. This deeply confused me for a moment, but then I realized that this took place in the past, when Hal Jordan was a pretty decent character (DUIs, statutory rape, doing nothing for the brown skins--you know, recognizable flaws).