So, a pulley drive with the drive pulley having 1cm of diameter and the driven pulley 10cm of diameter would have something around a 10:1 reduction ratio.
However, I don't know if the same logic would apply to a compound pulley, assuming that the fixed pulley has 10cm of diameter and the movable pulley has 1cm of diameter, on top of that, the winch driving the system has 1cm of diameter.
Pulleys gain advantage by multiplying the constant tension of the rope by the pulley advantage. Gears and belts give an advantage to the torque of the sheaves/gears, not the tension on the belt.
In your example, there is a ~2:1 advantage because there are two ropes pulling the weight up. Both ropes have the same tension, so there is twice the force on the weight, at the expense of half the motion. The belt example gives advantage because the sheaves turn at different rates.
