Your question is a little confusing. 2ds, or plain DS?
DS games I have:
Sim City DS
Pokemon Conquest (Imagine pokemon in a final fantasy Tactics style of gameplay, mixed with japanese warlords.)
I kinda suggest drawn to life.
I just picked up Sid meier's Civilization revolution (for $4.80 at gamestop

), which is a dumbed down, but still fun Civs game that can be beaten in the course of a night at low difficulty. basically it's supposed to be more streamlined.
But if it's actually the 2ds, aka the 3ds without the 3d?
Project X-zone is really nice. It made me happy seeing familiar faces, and got me wondering about some of the unfamiliar ones.
Rune factory 4 is nice. Live action hack and slash with leveling up for nearly everything.
tomodachi life is kinda fun in a very light gameplay way. you can level up residents, and such.
I'm not sure where Style Savvy trendsetters falls into as a genre, but it's pretty rewarding, and you expand your arsenal bit by bit. If you can get past the girly theme, it's a rewarding game.
Zelda Four Swords Anniversary edition was free at one time.
Senran Kagura Burst is good. It has character growth, unlocking stuff, etc. but is a side scrolling brawler. Under all that fanservice is a good game with some oddly good writing.
Scribblenauts in general is good. I liked Unmasked for the joys of reading bios, and stuff.
Samurai Warriors Chronicles is nice. Some leveling up to be done, some weapon enhancement stuff, lots to unlock, and it's got a lot of that Koei Warriors series feel in gameplay.
Sims 3 pets is, well, a sims game.

You can even build a home, though it's not as rich a building system as PC, or even most console releases.
I'm trying to be a little unconventional in my suggestions, mind you. Of course there's the pokemons, and fire emblems, and so forth.