Another prioritization schema you can use is to score each feature using over value--benefit and penalty--and cost and risk. The picture below is a sample of what this would look like:
Each criterion is scored 1 through 9, 1 being low and 9 being high. Benefit criterion is obvious; this is how the feature would add overall value to the system, organization, stakeholder group, revenue and profit, etc. Penalty is the "price" the organization would pay if the feature was deferred. Benefit and penalty together provides an overall value score.
Cost criterion is the cost to the organization of implementing the feature or requirement. And risk is the overall risk to the system in implementing a feature.
You can alter the weights of each criterion so long as they equal 100% for both benefits and costs and risks. In the picture, they are all weighted equally.
The math behind the tool is the criterion score x the weight and then adding the products together for both the value side and the cost and risk side. Then the sum is simply divided by the total sum of all the scores to arrive at the relative total.
Example math for item 1 is ((9*50%)+(9*50%)/110.5) = 8.14%. Cost side is ((3*50%)+(7*50%)/90.5) = 5.52% Then, the relative benefit is divided by the relative cost: 8.14%/5.52% = 1.47.
Simply sort from high to low and you have your priority.
This graph shows how the tool works. You can see that the high priority item scored higher in value and lower in cost and risk and then vice versa for the low priority items.