Chrono Crossing is really close for me between two games. Since one of them is Dark Souls and everyone will be talking about it, I'm going to pick Kirby's Return to Dreamland. It's my favorite 2D platformer of 7th gen, the mechanics felt very similar to Super Smash Bros, but built with a Kirby game which made it feel unbelievably polished and addicting.
Kirby's new super abilities were also a blast to use and gave some fun optional puzzles which led to secret areas. The secret areas were surprisingly tough and gave me a very fun challenge that was completely optional, which many KIrby games hAve tred but none succeeded as well as RtDL. Multiplayer was also a blast, letting the other three pick their own Kirby, King Dedede, Meta Knight, or Waddle Dee, each controlling different from the other. Dark Souls gets a ton of love for its challenge but I respect Kirby more for managing to give a game any kid can beat but hardcore gamers can still come away satisfied with the challenge.
Btw if I put my pick for 2012, it would have been Mass Effect 3. On one hand the ending was disappointing, but on the other, drunk Tali.
