Gravitational pull must be measured in units of ...

'Pull' is force, so units of force must be used to describe it. But that's not a very usefull way to describe the gravity on, say, the surface of a planet, because the amount of 'pull' depends on what's being pulled. A much better way to describe the gravity of, say, a planet is in terms of its acceleration, since every dropped object accelerates at the same rate on the same planet, no matter what the object's mass happens to be.