Taking a look at Wikipedia's List of Best Selling Game Consoles reveals the Nintendo DS taking first place in the highest selling handheld ever, and is merely second in the highest selling video game system ever.
It's had a number of huge titles on it, but there's one thing people seem to forget in terms of the DS's innovation. The touch controls.
The Nintendo DS hit the shelves in 2004 with its stylus and touch screen. Sounds like something else in the market today, right? Cue the smartphone. Specifically, cue the first iPhone, which was released in 2007.
That's right. The Nintendo DS pioneered touch screen gaming three years before the mobile gaming phenomena hit. In fact, even if the DS wasn't a direct influence on the iPhone's design, it had to at least have some hand in the inspiration of games that were to come to the mobile market.