Why ask this question on a site where most people already own more pins than four pins?
Are you expecting people to name their four favorites of the games they own, or do you think there are a lot of people who would rather have some pins other than the ones they own now?
The thirteen pins in my game room are my 13 favorites. (While I view MM as the best pin I don't own, W?D was a must-have to me and MM wasn't.) If limited to only 4 I would keep BBB + MB + SS + AFM.