Some I know: old Shiren games, Dragon warrior/quest in the West for a while, most "newer" SuperMemos.
One factor can be that the duration between one and the next lasted a short time.
Or some products are just not advertised! Or it may not be the goal.
Rather, most poorly marketed products, by the law of availability heuristic, I don't even know exist (some cases may involve it getting more popular THEN I know. For the eternal unknown, I may not know.)