(Packs a dank bowl) "Like, what IS a game when you think about it, MAAAAAAAN"
Alright, so neither of these titles has anything resembling a "win condition" or "level progression" but both let you get your groove on in tiny portable chunks. Electroplankton was a collection of audio-visual toys that created an evolving soundscape as the ephemeral little plankton grow and bounce in response to your various inputs. It's a delightfully zen-like experience that gets your alpha-waves flowing (note: find a neuroscientist and confirm that this makes any sense whatsoever). On the other hand Korg DS-10 is literally just an emulator for an old synthesizer. Sounds cold and unpleasant, but after a little bit of fiddling and free experimentation you'll soon find yourself making loops and songs and partying like an unattended child in a Guitar Center. They're the only two titles for the system that can do THIS:
WayForward's crack at the classic and notoriously difficult side-scrolling shooter has you dodging, ducking, and praying to the Lord Almighty for a spread cannon. With platforms and projectiles coming at you from both screens, the learning curve is harsh. Yet not as mind-destroying as previous entries... until you bump up the difficulty. It's not a long journey, but instead a wild ride. ALSO, you can unlock the roms for the original Contra and Super C, so eat it, Nintendo eShop.
Clover Studios was the development house that Capcom started for the purpose of making cult classic games that cost way too much to produce. When tasked with adapting the flashy fast-paced action of Viewtiful Joe to the underpowered DS hardware, they used every trick in the book to make it work. Joe's journey through a movie backlot under siege requires simultaneous use of the touchscreen and gamepad as you use your powers to fight mooks and solve platforming puzzles. There was also a clever mechanic where during combat sequences, the top screen zoomed in on your character for precise combo timing, but the lower screen gave you a zoomed out perspective to keep track of the bad guys around you. Clever workarounds and intense gameplay delivered what felt like a full-sized console experience in a portable package. Henshin a-go-go, baby!
Demons and lolis and penguins, oh my! A port of the PS2 Tactictal RPG, Disgaea DS brought along all the humor and versatility of the full sized release, just with way less voice acting. Set in a mythical underworld, you build an army up and train them as you seek to claim the throne and defeat the machinations of Heaven. For anybody who loves tactical RPGs, you already played this and all the sequels, but if you're not a fan of the genre, this series has enough slapstick and metahumor to keep you entertained as you learn the myriad of systems in play. Also, it's the only game on this list to feature knife-wielding penguin mooks.