Correct me if I'm misunderstanding the topic, but Mother seems like the opposite in that a lot of people know about it (largely due to Smash), but most of those people haven't played. They really should though; that is a fantastic series.
I'd definitely say Castlevania would probably be a big one for this topic. That franchise was pretty big back in the day, with the first game generally regarded as one of the NES classics, while Super Castlevania IV and Symphony of the Night usually rank highly on those "Best games of all time lists." With that said however, I've only met one person in my life who has played a game in this series. I don't know, I may just be looking in the wrong places, but I would think that more people would've played at least one of these games with how well known they are and how many there are.