In Apple's App Store Rewind 2011, they named the iPhone/iPad App and Game of the year for 2011. For iPhone, the Game of the Year was Tiny Tower, and the App of the Year was Instagram. For the iPad, the Game of the Year was Dead Space, and the App of the Year was Snapseed.
More details about the games can be seen in the snapshots of the iTunes store shown below (click to enlarge):
Source: iTunes (launch iTunes, open iTunes Store, then goto App Store and you will be able to view the App Store Rewind for 2011)