Um, as I understand it, it's a ratio of weight to drag. If two things have equal drag, the heavier will fall faster. This is why if two people are skydiving, and one is face down, the other dives, the diving person will fall faster (less drag), roughly the same weight. But add weight, it should fall faster. A chunk of solid iron in the shape of a man should fall faster than a man (If I recall correctly).
This is basically incorrect. The rate at which a heavier object falls faster is pretty inconsequential. In a vacuum, the force of gravity between two masses will be the total mass of the object. But of course, the gravity of something the size of a planet on something the size of a man is going to completely over-power the gravitational effect in the opposite direction. So much so that Galileo was able to "prove" that heavier objects don't fall faster. Unless you really want to calculate the effect of a single man's gravitational effect on something the size of a planet.
In a physics engine for a game, you would basically consider the ground a fix point mass at which two objects should fall at the same rate, then you'd have to calculate drag to show the rate it would slow.