How come the one to the right looks fine and the two broken ones are mangled? I'd figure that the one to the right would be showing some signs of abuse even if it isn't busted off? All valve springs and keepers are the same (or should be).

Tight valve clearances cause the valve to stick and then the piston hits the valve and bends it. Never heard of a sticky valve causing the top of a guide to shear clean off like that. Even a 'stuck' valve will pull right out of the guide. They can't weld themselves together.