What are the differences in IV inheritance between the generations? I have been doing some IV breeding in Emerald, but HP, and Def. have a lower chance of being passed down to the child, and I'd like to breed defensive Eevees and Koffings. Now I wonder in which game I should best continue breeding, but neither Smogon's breeding guide, nor Bulbapedia go into detail regarding changes between versions and generations.

I know that Gen IV and up has stat-specific items which you can give your Pokémon to hold, ensuring that they pass down that particular IV of theirs, but that is the extent of my knowledge.