In addition, if you have a lot of people at work/school who have a DS, Mario Kart is a must have, it's currently the best multiplayer game on the system. I haven't played much of the online though. If looking for a game with a strong online community, Animal Crossing is the best bet, and there are lots of dedicated web groups around. For advanced online play and ridiculous amount of learning (seriously, this game just hurts the ego to play when you get shot to death in the head like 60 times in a period of about 3 minutes) try Metroid Prime Hunters.
Zelda: Phantom Hourglass is also a good pick judging on comments from everyone I know who has played it. There are also a lot of survival and adventure titles such as Lost in Blue, Sims Castaways, Trace Memory, and Hotel Dusk which are all good picks. Elite Beat Agents is one of the most creative music based games I have ever seen (it's essentially a comic that moves forward and changes depending on how well you do, plus it has Madonna!)
If looking for adventure RPGs, there are some good available now, but there's a tidal wave of great ones coming up next year including remakes of SNES Dragon Quest and Final Fantasy titles; not just GBA-calibur remakes, but with 3D graphics, video (and no load times), redone scripts, added scenarios, gameplay improvements, and voice acting. Though this isn't to bash GBA remakes of games, the FF1-6 remakes on GBA were all done quite well (though nothing could really save FF2 in my opinion, I do still plan to give it a nice shot still, and FF3 is fully redone for DS rather than GBA), in addition the Tales of Phantasia remake is quite good as well, it is better than the SNES one, but not as good as the PSX one (which I haven't played, but have seen and read enough about) and it is the only official English version.
Though, as mentioned above, the games that made the largest impact on me with the DS were Capcom's Phoenix Wright games. They aren't an RPG as we typically know them, but do contain more roleplaying and much more dialogue than those.
In addition, Final Fantasy 12: RW was released for DS recently, and from what I hear, despite not being as cinematic, it is a more fun and entertaining experience than the critically acclaimed PS2 title. Of course, my only source for this so far are the local female gamers, so we'll have to see. It has received quite decent reviews though.
So yeah, mostly what I play are adventure/RPG type games on DS, and while the genre of non-violent adventure titles isn't as well reviewed as others, this has become my favourite genre of videogames and can only hope to see more.
-Insert Inspiring Quote-
