I hate to start posts like this with a disclaimer, but in this case I really feel I have to do so.
You see, although I've played a ton of DS games over the last few years, I've yet to play a number of the titles that tend to be included on lists such as this--titles like Henry Hatsworth in the Puzzling Adventure, Kirby Mass Attack (which is on its way to my doorstep), Solatorobo and The World Ends With You (which I'll be picking up shortly).
Still, I've played and enjoyed enough of the system's releases that have been overlooked by the masses that I'm fairly confident the following list--which is organized, for once, in reverse alphabetical order--will be helpful to at least a few game-starved DS fans.
1. Rhythm Heaven--Sure, this is hardly an unknown game, thanks in large part to Nintendo's use of Beyonce in its TV ads, but it also hardly lit up the charts. That's too bad, because it's one of the funnest, wackiest games I've ever played. It also includes one of the best soundtracks you'll ever hear in a handheld title. It's horrendously cheap these days, so you may want to pick it up now if you've yet to give it a try.
2. Retro Game Challenge--This one has received a lot of press since it was released in 2009, but even then it didn't make enough for the folks at Xseed to translate and release its much-wanted sequel. Why is that unfortunate? Well, Retro Game Challenge is chock-full of witty writing, which ties together a bunch of well-made retrotastic titles that call to mind the classics of old (like Dragon Quest and Galaga). If you're a fan of such games, you're sure to quickly become a fan of this one, too.
3. Kirby: Canvas Curse--For me, this was one of the first games to really show the potential of Nintendo's dual-screened handheld, thanks in large part to its intriguing stylus-only control scheme. Sadly, I seem to be one of just a handful North Americans to feel that way about the game, as it was all but ignored by my brothers and sisters despite the fact that it bore Kirby's name (usually an attention-getter in the States, as far as I'm aware). Used copies can be found on eBay for a song, though, so it's not too late to snatch one up if you're at all into innovative platformers.
4. Final Fantasy: The 4 Heroes of Light--I'm sure some of you who have been coming here for a while are sick of me mentioning this game. Sorry about that. I can't help myself, though, as I thought it was an absolutely wonderful RPG. I seem to be one of the few North American gamers who feel that way about the title, though, which is why I'm bringing it up again. Really, if you love RPGs like Final Fantasy IV, V and VI, you'll love this one, too--although you may not love the way it places limits on your ability to store items and weapons.
5. Daigasso! Band Brothers--I honestly believe that if Nintendo had localized and released this accessible and surprisingly addictive music title in Europe and North America in 2005 as originally planned, it could have become quite a hit among so-called casual gamers. Instead, the company dragged its feet and, in the end, dropped its Western release altogether. It did release this game's sequel, Daigasso! Band Brothers DX (aka Jam with the Band), in the former region--but it waited nearly two years to do so. (The game hit Japanese store shelves in 2008, while it didn't hit European ones until 2010.)
Honorable mentions: 999: Nine Hours, Nine Persons, Nine Doors; Etrian Odyssey; and Freshly-Picked Tingle's Rosy Rupeeland.
Are you a game-starved Wii owner, too? If the answer is "yes," keep an eye out for a similarly titled post that focuses on five of that system's should-have-been-classics. (Don't worry, you won't have to keep an eye out for it for very long, as I plan on publishing it tomorrow.)