I enjoyed Mystery Dungeon but disliked the main games.
Coliseum and X.D. on the Gamecube were rather engaging storywise also. The mechanics were similar to the main games with the coli and xd games, but they threw in new concepts and actually had a decent storyline.
Mystery Dungeon was just really really really enjoyable.
If a game doesn't have either extremely engaging gameplay or an extremely engaging story then it won't interest me.
Rogur Legacy is an example of a game that seems completely storyless at first and has rather fun gameplay but then pulls a fast one and stuff it has been hinting at the entire game cumulates into a story. It also had a bunch of those little touches that make a game amusing. Such as one of the journal entries questioning why mushrooms and plants were giving coins and roasted chicken.
Another game series with little touches, although they started to vanish later on was Borderlands one and two, they just had these tiny little touches hidden throughout the game that I'm pretty sure very few people would notice but they did them anyways and the game felt immersive because of them. Expecially near the beginning of 2, there were several little ones that made me empathize with Claptrap, although he was an annoying character, he had reasons for that, if you looked, you would find them, they managed to build up empathy for the most annoying character in the entire game purely with little hidden touches.
Games rarely do that, and although I dislike some game mechanics in Borderlands, I can say I thoroughly enjoyed myself because the designers somehow managed to flesh out the majority of the background characters with small little additions to the world.