Look, you and I both know why you're here. It's to find out what we picked as the best Nintendo DS game of 2009, right? OK, good. With that fact established...
Giant Bomb's 2009 Nintendo DS Game of the Year
"Hey," you're thinking to yourself, "you guys picked a game starring Mario and Luigi and made by Nintendo for your DS game of the year. Big effing surprise!" But it was a surprise that Bowser's Inside Story turned out as well as it did. The last Mario & Luigi game (and the first one on the DS) Partners in Time went through all the motions of this delightful, irreverent RPG series, but it didn't really recapture all the brilliance of the first game, Superstar Saga, way back on the Game Boy Advance. So you'll excuse us if we didn't have the highest expectations for this second sequel.
Hey, we're happy to be proven wrong! It was enough that Bowser's Inside Story offered the most refined set of RPG mechanics yet in the series, with Mario & Luigi's traditional fast-paced, reflex-based combat reaching new heights and really invigorating your progression through the game. It didn't hurt that the quality of the artwork improved by leaps and bounds over the previous game. The expert back-and-forth balance between sequences starring Mario and Bowser did a great job keeping the momentum of the story rolling, too. Oh yeah, did I mention that at several points you fight a castle?
It was really the quality of the writing and humor in Bowser's Inside Story that pushed it over the top, though. Nintendo's localization group just went above and beyond what was necessary to get an RPG translated and playable in English, crafting lovably ridiculous humor and injecting so much personality into the game's characters that it would be worth playing through just to see what ridiculous scenario would unfold next. You expect a certain level of quality with every game Nintendo releases, but it's fair to say none of us expected Bowser's Inside Story to be as good as it is.
Runners-Up: Grand Theft Auto: Chinatown Wars, Rhythm Heaven