It's between Odyssey and 3D Land for me. 3D land was such a shockingly good and enjoyable game that felt like it came out of no where. The post game content on that game was INSANE for Nintendo, so I'm giving it to them and I see as of now I'm the only one that voted for it lol oh well.
I was anxiously awaiting Uncharted 3 in 2011 and picked up 3D Land for the 3DS around the same time. I was excited for Mario too, but I didn't expect it to keep me from playing Uncharted 3 for weeks (extensively anyway). I remember one night booting up my PS3 with the intention of playing Uncharted as I was "finishing up" my play session with 3D Land. Hours past as Uncharted remained on the title screen with me feverishly playing level after level of Mario.
I did like 3D World quite a bit more, but 3D Land is a gem as well.