When I was in Brazil teaching the project portfolio workshop, one of the participants explained that his organization sometimes did a form of gold/silver/bronze comparison among the projects.
Here's how it works. Everyone wrote their project names on stickies. The first cut is everyone self-assigns their projects to Gold, Silver, Bronze categories. That's right, everyone does a pair-wise kind of comparison before everyone else adds their projects to decide if their projects are #1 projects, #2, or #3.
Now, everyone puts their stickies in Gold, Silver, or Bronze. Silently, they divide Gold, Silver and Bronze into thirds (Gold, Silver & Bronze), and continue, dividing into thirds, Gold, Silver & Bronze) until all the projects are ranked.
I would not do this with more than 30 or 40 projects. I would also not do this without a highly collaborative team who has been doing project portfolio management for a while, who is accustomed to developing a ranked project portfolio. But if you are such a team and you are looking for a new way to rank your project portfolio, consider this.