I haven't played the game in such a long time (not on my 3Ds in general) but I used to no-life it a lot back in primary-school. I remember having a small group of friends which we scrambled together during the summer holidays in Spain. We would play the game together for hours at the time (instead of actually enjoying the vacation). Those were great times. Metal-Mario was by far my favourite character to play with and I would usually also play with the Dasher car with golden wheels under it. I played a lot of different games on my 3Ds during that time but Mario Kart 7 and Super Mario 3D Land were the only ones I've ever really taken seriously.
Before I got my 3Ds I mostly used to play on my Wii so I have a lot of great memories from Mario Kart Wii too, although probably not as many as from Mario Kart 7. I also used to play a lot of Super Mario Galaxy 2 (dang I loved that game) although I remember not being able to set it to Dutch so I constantly had to call my dad into the room to translate the English dialogues for me. This game also didn't really seem to have an end to it as well so that's probably why it kept me hooked for so long.
I also reckon playing a lot on my gameboy (even before I had my Wii) and having like a box full of games for it including some of the original Mario games from the 20th century. I basically had too many of those games to individually mention but believe me when I say I had a great time playing those too!