The importance-satisfaction matrix, or gap analysis, was discussed by Dan Olsen in
The Lean Product Playbook (a must-read for PMs).
Given a list of initiatives to prioritize, graph importance of user need on the y-axis, and user satisfaction with current solutions on the x-axis. Initiatives with a high importance to users and low available substitutes on the current market means there's a high-growth opportunity for the team to pursue. If it's of high importance, but there exists competitors, it may still be worth entering the market. However, if it has low importance, PMs should completely ignore that initiative.
If plotting on a scale from 0-100%, use the formula Value = Importance x (1 - Satisfaction) to rank initiatives.