Yeah, I'm going.      
 
I'm heading cross country to what may be the single most important event in our lifetimes.  
Okay, maybe that's a bit hyperbolic, but it's going to be awesome.  
However, the trip involves roughly 20 hours of... Not so fun. In fact, it's mostly sitting in a completely stationary position for a while.  
Luckily, I have a way-too-huge portable collection. So big I have no idea what to play through during my trip. 
So, here's my collection list, complete with a progress report on each. I'd prefer to start (and finish) something completely new over the weekend.  

Personal DS collection

All the games I own for my favorite console

	1. Phoenix Wright: Ace Attorney - Trials and Tribulations Finished.
	2. The World Ends With You Finished.
	3. Jump Ultimate Stars Finished.
	4. Elite Beat Agents Finished.
	5. Castlevania: Order of Ecclesia Finished.
	6. Phoenix Wright: Ace Attorney Finished.
	7. Valkyrie Profile: Covenant of the Plume
	8. Knights in the Nightmare
	9. Exit DS
	10. Custom Robo Arena
	11. Grand Theft Auto: Chinatown Wars
	12. Luminous Arc 2
	13. Suikoden Tierkreis Finished
	14. Fire Emblem: Shadow Dragon Finished
	15. Avalon Code
	16. My Japanese Coach Non-Game
	17. Jam Sessions Non-Game
	18. WarioWare Touched! Finished.
	19. Tetris DS Finished.
	20. Sonic Chronicles: The Dark Brotherhood
	21. Sonic Rush played.
	22. Rondo of Swords
	23. Professor Layton and the Curious Village Finished.
	24. Pokémon Diamond/Pearl Finished.
	25. Planet Puzzle League Finished.
	26. New Super Mario Bros. Finished.
	27. N+ played.
	28. Metroid Prime: Hunters Finished.
	29. Mario Kart DS Finished.
	30. Lunar Knights
	31. The Legend of Zelda: Phantom Hourglass Finished.
	32. Kirby: Super Star Ultra
	33. Izuna: Legend of the Unemployed Ninja
	34. Izuna 2: The Unemployed Ninja Returns
	35. Final Fantasy III Finished.
	36. Final Fantasy IV
	37. Disgaea DS God damn this game.
	38. Contra 4 played.
	39. Chrono Trigger Finished.
	40. Arkanoid DS Finished.
	41. Animal Crossing: Wild World Played.
	42. Advance Wars: Days of Ruin Finished.
	43. Apollo Justice: Ace Attorney Finished.
	44. Phoenix Wright: Ace Attorney - Justice For All Finished.
	45. Shin Megami Tensei: Devil Survivor
	46. Luminous Arc Finished.
	47. Lock's Quest
	48. Might & Magic: Clash of Heroes Finished.
	49. Ninjatown
	50. Fate/stay night Finished.
	51. Nostalgia
	52. Sands of Destruction
	53.
	54. Glory of Heracles
	55. Osu! Tatakae! Ouendan Finished.
	56. Moero! Nekketsu Rhythm Damashii Osu! Tatakae! Ouendan 2
	57. Henry Hatsworth in the Puzzling Adventure
	58. Infinite Space
	59. Pokémon HeartGold/SoulSilver Finished.

" Etrian Odyssey 3? I haven't played it yet, but the first two were good. You could also try the other two DS Castlevania games, Portrait of Ruin and Dawn of Sorrow. "

I've been using My Japanese Coach, and I've found it helpful. Some of the games used for retention are kind of lame, but it's effective enough. Ace Attorney Investigations: Miles Edgeworth is really awesome, and would probably melt the 20 hours away; a very engaging game it is. Chinatown Wars and FFIV are also excellent choices. I guess engagement is the #1 thing here; something to hook you immediately, to make you forget that you're ass is numb.

" I've been using My Japanese Coach, and I've found it helpful. Some of the games used for retention are kind of lame, but it's effective enough. Ace Attorney Investigations: Miles Edgeworth is really awesome, and would probably melt the 20 hours away; a very engaging game it is. Chinatown Wars and FFIV are also excellent choices. I guess engagement is the #1 thing here; something to hook you immediately, to make you forget that you're ass is numb. "

I would definitely recommend Chinatown Wars. The gameplay is probably around 15 hours, but there is a whole lot (and I mean a WHOLE LOT) of optional content - sidequests, races, drug dealing minigame, etc. This should keep you interested throughout the trip.
One of the things I loved about Chinatown Wars is how varied it is. In one mission you participate in illegal racing, another one is delivery, another time you need to blast some gangsters. There is a sniper mission, there are getaways, police pursuits, bombings. It's all in there.
Also the way GTA: CW uses the touchscreen is neat - basically all touchscreen minigames can be played with your finger only (no need to remove the stylus for a 5-second minigame). 
 
 Now, about your other options:

- Infinite Space - this game takes well over 30 hours to beat. One of its biggest disadvantages though is that it has no mission log, so if you put it down for, say, a week, you will not know what to do next when you pick it up again.
- Devil Survivor - Really good, if you like tactical RPGs. The game is really good, nice storyline, slightly annoying but bearable emo dialogues, lots of depth. However, for me it got kinda repetitive after around 20 hours.

Oh, and BTW: how did you manage to finish Tetris???