Cookie score.
Count how many times each player is taken across all 96 teams. Then, for each person's roster, average that number among the 25 players on a person's roster. That average (called the "cookie score") is often a weighted average based on salary. The higher the cookie score, the more commonly selected players one has on his roster.
If all 25 players on your roster were taken only once (by you), your cookie score would be 1.0