I didnt play a lot of 3DS but:
- Monster Hunter 3U (my fave)
- Monster Hunter Generations (Only one on my list I havent personally played)
- Fire Emblem Awakening
More importantly, DS:
- Castlevania Order of Ecclesia (if you only play one this is it)
- Castlevania Dawn of Sorrow (not fond of Portrait of Ruin)
- The World Ends With You
- Bowsers Inside Story
- Advance Wars: Dual Strike (best in the series)
- GTA Chinatown Wars (only gta title I got into, loved the top down view and drug selling system)
- Rhythm Heaven
- Dragon Quest V: Hand of the Heavenly Bride (Best JRPG and one of the few that managed to keep me hooked)
- Mario & Luigi: Partners in Time
Damn, after writing out these games, I want to really try to get an Emulator on Steam Deck working and play me some DQV or Mario & Luigi.