It's arguably the best portable format ever for games, and so far the most popular. Boiling down five games wasn't easy, but if you read my Gamecube list you'll know how much of a sucker I was for Wind Waker, a game Nintendo built on well by delivering an adventure that really built around the Nintendo DS hardware. The result was an absolutely magical adventure that would not have been possible on any other format.
The single Nintendo series I miss the most is Advance Wars, and nowhere was it better than in Dual Strike for the Nintendo DS from 2005. It had everything we loved about the original, but again with clever use of the dual screens and a plethora of new features that elevated the playability. This is one of those few games that time can't touch, and it's just as fun today, almost two decades later, as it was when it was first released.
Actually, it should have been known as Osu! Tatakae! Ouendan, but it was never released in the West and was turned into Elite Beat Agents instead, one of those games that really wouldn't have been possible without the Nintendo DS and which not only made the most of the format but offered something completely new in the way of wacky Japanese humour. The basic concept is to cheer people on as they do things - and this mildly bizarre idea captivated an entire gaming world at the time. For good reason.
By this time Nintendo had moved on to making three-dimensional Mario games, but after over 15 long years many people missed the 2D adventures. In 2006, Nintendo decided to listen to this and released New Super Mario Bros., showing that they still know how to make platform games in a way that beats everyone else. The classic Super Mario formula was given so much gameplay innovation that the concept felt fresh again, and since then Nintendo has regularly returned to the two-dimensional versions of the plumber brothers. An absolute must in your Nintendo DS collection.
Just as with the Gamecube, the best game to come to the format doesn't come from Nintendo themselves. Instead, Rockstar offered this in Huang Lee's unexpectedly raw adventure that contained all the ingredients that made the world love Grand Theft Auto so much. Rockstar neatly avoided the trap of trying to cram in as many heavy graphics as possible and made an exclusive action-adventure tailored to the format's hardware that perfectly utilised its graphical capabilities and features. In this way, the stylus became an integral part of your drug smuggling and burglary operations. In addition, other features were used in clever ways such as whistling for a taxi using the microphone. The fact that an adventure like Chinatown Wars could even fit on a tiny Nintendo DS cartridge was and remains a mystery, but while it seems somewhat forgotten today (except for a minor mention in Grand Theft Auto IV), it stands out as one of Rockstar's finest moments.