There are a lot of monster catching games, mostly aimed at old fans fed up with the current state of pokemon. One I played and really enjoyed is called cassette beasts. You can scale the difficulty so that enemy levels scale based on your level, it's also moddable so people can add new monsters, modes, etc.

Just finished hypnospace outlaw, great game, you moderate internet pages in a fictional 1999, so if you feel nostalgic of that time the game might interest you. I enjoyed the story, though the ending was a bit anticlimatic, at least compared to what started the last arc of the game