I have NDS so I could recommend lots of good NDS games... but buying NDS at this time of day? Really, I highly suggest that you don't. Don't buy it now. If it's yesteryear, then it's ok. But now? You'd better be patient and wait for PS Vita to be launched. There should be a price drop for PSP (and hopefully, N3DS and/or NDS too).
Again, if you want to buy PSP, you'd better wait for PS Vita. If you want PS Vita, I'd recommend you to wait several months after its launch.
Whichever you choose, IMO, right now is not a good time to buy a new handheld console.
Anyway, if you insist on buying NDS, then here's my list:
- Avalon Code is a good game, buy that if you like Action RPG
- Resident Evil DS is pretty good. Buy it if you haven't played RE1 for PS to the death.
- Princess Debut sucks, don't buy it, really... It only good for several hours and after that, capital boring.
- Harvest Moon DS is ok. Buy it if you love Harvest Moon game and haven't play any other modern version to the death. If I'm not mistaken, this one have more girls (about 8-10?)so it should be ok... But please remember that Natsume release new Harvest Moon game almost each year. So you might want to look for a newer Harvest Moon game.
- Rune Factory is another good game. It combines Dungeon exploring RPG segment into Harvest Moon, and it's in 3D. So buy it if you do love RPG games... and Harvest Moon game. Remember that there is Rune Factory 2 for NDS.
- Atelier Annie is a good game. It's a decent Atelier game with focus to developing island (kinda like Atelier Meruru). A definite buy if you like Atelier game (like me, hehehe...)
- Trauma Center (1&2), officially it's a sim/VN, but in reality, it's more to fast-paced arcade operation game (with minimal VN elements). It's very hard and fast. Don't buy it if you have slow reflex or slow finger.
- If you prefer the slower one, try Hospital Affair. It's ofen compared to Trauma Center and doesn't sell well because it's very Visual Novel, not an operation sims. Well, they are right but that doesn't mean this one is a bad game. It's slow paced and the operation section is not as hectic as Trauma Center. It also have 3 endings and 3 date-able heroines.
- Cooking Mama series is a must for any NDS owner. It's pure fun. There are Cooking Mama 1-3 and the latest being Camping Mama which is a spin off (Cooking Mama 4 would be released in N3DS). Go straight to Cooking Mama 3. You wouldn't miss much by not playing the prequel.
- I don't play Pokemon that much... But all pokemon play more or less the same, and completing them all would take a good chunk of your life. It's a good game and a good fun... if you love Pokemon game that is. Just play the latest Pokemon (Black and White). You won't miss much by not playing the prequel too.
- Another must have game for NDS owner is Phoenix Wright series. There are Phoenix Wright 1-3, Apollo Justice, Milesedgeworth Investigation 1&2 (but the second game is still in Japanese). You have to buy them all if you are a VN lover... which I think you are, since you're in this forum.
- If you love Phoenix Wright series, then you have to buy Ghost Trick. It's from the same creator. You'd definitely love it. It's very original and have a good story.
- For VN lover, you'll also want to consider CING's game: Trace Memory, Hotel Dusk, and Last Windows. They're all VN with emphasis on creative puzzle that utilize all NDS features (touch screen, mics, dual screen, etc).
- 999 (9 People, 9 Doors, 9 Hours) is another must title for VN lovers. It's a bit heavy, dark, and gory... but otherwise it's an great game with excellent story. Two words, BUY IT.
- If you love sci-fi space RPG, try Infinite Space. It have excellent story and good spaceship building mechanism, but it involves lots of grinding...
- Suikoden Tierkreis is also another to consider if you love RPG. Being the only Suikoden in NDS, you don't have much option... It's Suikoden, so you know what you'll get, right? 108 characters. This time, the story spans multiple dimensions. And from what I know, this one is spin-off and doesn't have connection with main series timeline/story.
- Chrono Trigger is remade in NDS, so if you haven't played Chrono Trigger 30 times too many (I did) you'll probably want to try this one. NDS version uses PSX remake version so you'll get FMV along with additional dungeon and some minor bonus feature.
- Again, there are multiple remake version of early Final Fantasy in NDS. They have flashier 3D graphics, but it still the old traditional RPG, so you may not like it. It's FF so you know what you'll get.
-Radiata Historia is a must-get RPG for NDS. It's traditional RPG blends with modern one. It's like Chrono Trigger since it uses time-travelling concepts... and it's good in use that concept. Buy it, it's a MUST.
- If you love sim dating game, NDS have Tokimeki Memorial for girls series. But it's all in Japanese. I heard they make English patch but I haven't try it yet...
- NDS also have the notoriously famous Love Plus (and Love Plus Plus). If you have flash cartridge, you could "patch" the game and you could play it in ENGLISH >_< Don't end up marrying this game, 'k?
- If you love Okami in PS2 or Wii, then try Okami-den. It's a good game and this time you finally get to use stylus to use the magic ink. But don't compare Okami-den with its PS2 counterpart, you'll be disappointed (like me...)
- I know you don't like sports game, but you should at least try Inazuma Eleven (1-3, 1 is alrady localized). It's very RPG and it's very dramatic, with people can shoot like a cannon ball and the keeper have god hand moves. It plays not like Fifa or Winning 11. Instead you draw line/tap where the player should run, pass, and shoot. So it's more like strategy game.
- If you love robots/mecha and strategy, you'd want to try Super Robot Taisen (W/K/L). You could find various mecha from various anime in this game, like Wing Gundam, Jeeg, Mazinger, Getter Robo, Virtuaroids, etc.
- Unfortunately, there's no Fatal Frame in NDS. Fatal Frame 1-3 is in PS2 (and XBOX) and the fourth is in Wii. That's it.