Super Princess Peach- a DS game that is often overlooked for having Peach as the star. The soundtrack is good, the controls, are a bit confusing at first, but once you get used to it, the game is very fun. A lot of people avoid this game because they think it's bad, when it really isn't.
The Legendary Starfy series- This series is obscure because most of its games except for the 5th and final entry(released in 2009 overseas), have never left Japan. Although I have only played The Legendary Starfy, I feel that others don't know the series because of its first 4 entries never leaving their country of origin, and 5th one being largely avoided by many. I find this very sad, as I enjoyed playing it when I did, even though I needed help to beat most of the bosses.
Digimon series- This was once a huge competitor to Pokémon back when the series first started up. This was because Digimon came overseas a year after Pokémon did(the former came to the west in 1999, while the latter came in 1998, a year prior), so both series were very popular at the time. Many kids collected the toys, and watched the show on TV. However, when it came to video games, Digimon was knocked out of the park by its main competitor, Pokémon. After the second season of the show ended, Digimon was completely overshadowed by Pokémon's sheer popularity, and has never been able to fight back. While the games are still being released and has some players, the show hasn't been seen overseas since the final episode of Fusion aired. Now, the series is somewhat of a blue moon, you rarely see it anymore these days, and you're lucky when you do see it again. Though I prefer Pokémon over Digimon, I can see why it became a victim of Pokémon's over-popularity, that it will never be able to recover from it, nor fight back against it now that its tried a few times without success.
Yo-kai Watch series- Like Digimon, Yo-kai Watch is a competitor to Pokémon. Though I've only played the first Yo-kai Watch game, and only watched a few episodes of the show, I ended up liking the series. However, right from the beginning, it became a victim of Pokémon's over-popularity. The series as a whole in the west hasn't been as successful as it is in Japan, and now, people rarely see it anymore here. Although I prefer Pokémon over Yo-kai Watch, I can see why it'll never be able to fight back against Pokémon, nor recover from being a victim of its over-popularity even though it has tried to do so without success.