Gee, this is actually a rather tall order, but it's not due to a lack of options! My favourite release so far would have to be Super Mario 3D World, as it was an absolute blast from start to finish. NSMBU, NSLU, and DKC Tropical Freeze are terrific platformers, and I've enjoyed Mario Kart 8 and Need for Speed Most Wanted U greatly as well. Pikmin 3, Batman: Arkham City, and The Wonderful 101 were also quite enjoyable.
On the eShop, the NES Remix series, Shovel Knight, Guacamelee and Ducktales Remastered were big hits with me. I'm very eager to play several games which I already own but have yet to begin, such as Darksiders II, Deus Ex: Human Revolution Directors Cut, Batman: Arkham Origins, Lego City: Undercover, Rayman Legends, and Zombii U.
There's also plenty to look forward to in the next 12 months as well!