I got a Wii U + New Super Mario Bros. U + New Super Luigi U pack for Christmas! I really like the challenges and Boost Mode (I believe that's what it's called...), even though I only play single player modes. I have decided to only start playing New Super Luigi U when I finish New Super Mario Bros. U (after all, it's harder!).
I really like Mario Kart 7. I've played Mario Kart DS before, and for a long period of time. I really like the Time Trials... and they're better in Mario Kart 7 because it downloads ghosts from around the world (if SpotPass is activated).
I've finished Mario & Luigi: Bowser's Inside Story before, reaching rank 40 with all characters, which is mostly why I got Mario & Luigi: Dream Team. I've finished it, but I've started Hard Mode and maybe I'm going to finish that too!
Oh, and I've also managed to get the max. amount of lives in New Super Mario Bros. 2! It's not what you're thinking... I've also got all star coins and moon coins, so I have the 5 stars (in the save file selection screen).
Other games I really liked: basically all games of the Super Mario series for DS and Wii. :p