I'm going to get a new DS game soon and there are so many fucking games on that thing I'm completely torn. I'm leaning towards Spirit Tracks of Phantasy Star 0, I'm looking for something with a lot of replay ability.

SMT: Strange Journey!

What games do you have, and what genres do you like?

PICROSS 3D

" check this out "

Zoo Keeper, my favourite puzzle game

I'll just add GTA: Chinatown Wars here.

Picross DS trumps Picross 3D for me any day, but both are still good games.

Civ Rev. It's hard to find now, but if you can find it it's bound to be a good deal. I saw it for just $10 the other day.

" check this out 
 
also, PICROSS 3D!!!!!!!!!!!!!!!!!!!!! "

All three Castlevania games. Dawn of Sorrow is my favorite, but they are all good.

Rhythm Heaven, Picross 3D and Elite Beat Agents are my go to DS games

The World Ends With you
Any of the Castlevania games although I enjoyed Portrait of Ruin the most
Clubhouse Games
Dragon Quest 9
I'm currently making my way through Four Heroes of Light, it's...  alright, so far
Any of the Professor Layton games
Final Fantasy 4
Final Fantasy Tactics A2
Suikoden Teikris
Valkyrie Profile
Advance Wars (the second one was good but not as good as the first)
Elite Beat Agents

There are other good ones that I just can't think of off the top of my head.  Also, that list thread that someone linked is fantastic.    

Hotel Dusk, if you don't mind a 20/1 story to game ratio. That may actually be generous.

... Oddly enough, Koei's Pop: Cutie clothing design video game.  I played this game for like 14 hours at my in-laws house last Thanksgiving.

" SMT: Strange Journey! "