I bought myself an N64 with my student loan (pretty standard, right?), mostly so I could educate my housemates about the likes of Conker's Bad Fur Day, Mario 64, Golden Eye.. because they really needed it. Decided to get Diddy Kong Racing out and got incredibly addicted. For a game you think would be aimed at younger children, the adventure mode is so bloody difficult; know how hard it is to collect all the silver coins and then still come first? you'd be suprised! The game is incredibly addictive but also incredibly frustrating. Took me a week or so but I had the game completed, wispig and all.
I consider it my greatest achievement of 2011, along with replaying FF7 to the point of utter completion, (I've played it millions of times, but never this thorough, every summon, every ultimate weapon, materia maxed, hp maxed), doing Emerald weapon was a joyous occasion.
tl;dr. Firstly, Diddy Kong Racing and it's awesomeness. Secondly, what gaming achievement do you consider, from this past year, to be your highlight?
Now, back to Banjo Tooie..