I'll go ahead and give you some recommendations but you can determine from the descriptions whether you think they'll be for you. For the 3DS:
* Devil Survivor: Overclocked -- This is a tactical RPG. It is quite difficult in parts, but offers many hours of play and is great if you like games in the "capture monsters and use them to do battle" subgenre.
* Heroes of Ruin -- A very accessible action RPG in the vein of the Diablo series. Lots of fun, not that difficult.
* Animal Crossing: New Leaf -- The most casual of casual games. You live in a town full of animal-people and do stuff like fishing, dig up fossils, write letters to the townspeople, improve the town by building new facilities, and you can decorate your house (and your character) with hundreds of different items (furniture, wallpaper, clothes, etc.) This is designed to be played a little bit each day. There's no real challenge to it, you just collect stuff and make your house pretty.
* Shin Megami Tensei IV -- Same general idea as Devil Survivor, but with a different setting. The mechanics are very similar, though there is no tactical grid to play on, just straight-up battles. Also a difficult game!
* Monster Hunter 3 Ultimate -- Another action RPG, though without much of a story. The thrust of this one is to hunt and kill monsters, then upgrade your gear so you can kill bigger and nastier monsters. Rinse and repeat. Very popular game but perhaps not everyone's cup of tea. It can be rather difficult.
* Fire Emblem: Awakening -- Arguably the best tactical RPG on the 3DS. Great story, great characters, and you can put your characters together to have kids with unique powers. Don't get me started. Not terribly difficult, in my opinion. It's at least easier than the Shin Megami Tensei games!
* Bravely Default -- If you liked the oldschool Final Fantasy games--I'm talking about 1 through 6--then you'll like this. It's the old formula with some interesting new twists and a decent story. It's also potentially more forgiving because it has adjustable difficulty, which the old games did not.
For the DS:
* Front Mission -- This is a port of the original SNES game. It's a tactical RPG with mechs that you can customize. Also has a pretty heavy (military-themed) story as such things tend to go.
* Chrono Trigger -- Another SNES port. This is a very story-driven role-playing game. If you never played the original, you are in for a treat. If you have, then enjoy the nostalgia. Still a great game after all these years. Not very tough, either.
* Might & Magic: Clash of Heroes -- This is what they call a puzzle strategy game. It's a lot of fun, pretty casual in general. I normally hate puzzle games but this one's very entertaining.
* Disgaea DS -- This is a port of a game from the PlayStation. Another tactical RPG. While I enjoy a wide variety of games, on the DS consoles I am a big fan of tactical RPGs. This one has a fun, often darkly comic, story. It also has very deep mechanics that will take some time to wrap your head around, but it's very much worth it.
* Infinite Space -- This one is hard to pigeonhole. It superficially looks like a space combat game, but it's more of a space combat strategy game, in that you aren't really controlling your ship in the sense of flying it around with a joystick. Instead, you command a crew and complete missions, and sometimes you get engaged in battle, which is almost a rock-paper-scissors affair in which you need to anticipate the enemy's next move so you can properly counter it. It's fun and has a good story, though it can be quite difficult.
* Final Fantasy III, Final Fantasy IV, and Nostalgia -- Separate games, the first two are both remakes of SNES-era games and the third is an original game using the same engine. Between them, I'd say IV is the best, owed mostly to its story. At this point I'd say III is redundant if you're going to get Bravely Default, since both use a similar job system that serves as the main gameplay attraction and Bravely Default's story is slightly less generic. Nostalgia has its own pretty decent story but I'm not sure anything else about it is unique enough to warrant a buy unless you are an obsessive RPG player.
* Radiant Historia -- This one, however, is a unique enough RPG for me to give an unqualified recommendation. It has a lot in common with Chrono Trigger, mostly in that it's a game about time travel. It has its own twist on the mechanic, though, and it's very intriguing. Difficulty-wise, it's tougher than Chrono Trigger, so you may want to start with CT.
I don't have my kids' games handy right now. They might have some stuff you'd find appealing--there are LEGO Star Wars games and things like that. I can check when I get back home next weekend.
Anyway, I hope you find at least one or two good recommendations in there.