Dragon Warrior Monsters was a Gameboy title released by Enix in 1998/2000. It was the first spinoff in the Dragon Quest series of games, featuring many of the same monsters from those titles, with the twist that in this game, you tame and battle the monsters.
It would be easy to write this game off as a Pokemon knock-off, but Monsters did many things to differentiate itself from the most famous monster-catching game of all time. In this game, monsters can;t be caught; rather, you give them meat throughout a battle, and if they so choose, they join you. This made obtaining monsters much harder to do. In addition, the monsters could only be commanded during regular battles. During the tournaments, which were required from time to time to advance to the next level of the game, your monsters fight independently, based on how you trained them and their personalities. Finally, the game used a much more traditional MP system for special attacks, playing much more like a Dragon Quest title than a Pokemon one.
All that, plus an in-depth breeding system, tons of extras to discover and an ever changing world that becomes more and more explorable as you progress through the game made this a game that helped define an underutilized sub-genre, rather than a mere clone.
The game went on to receive a mobile port and a 3DS remake – unfortunately these were both Japan only. We DID receive a sequel on Gameboy, and some new games to the series under the Dragon Quest Monsters: Joker brand.
So what are you waiting for? Go give Dragon Warrior Monsters a try!