Saying that Mass Effect 2 had the worst story of 2010 is INSANE. It might not have been the best, but it wasn't even close to the worst, and the writing was really good, which does make up for any small pratfalls in the main tale. What was the worst? Force Unleashed 2, maybe. I'm not far through, but it's shocking. Bayonetta was awful, and Vanquish - but I forgive it, because in Vanquish's case it's almost knowing - or, the translation is. Alan Wake's was pretty shocking - not for what it tried to do, but in how drastically it failed. Heavy Rain wasn't the worst, but it was noticeable as being bad - you put that much stock in story in your game, it had better be good enough to back itself up, and Heavy Rain wasn't.
However, my winner is Other M. It was so bad it actively forced me to stop playing, when I really wanted to continue - as a fan of franchise, and the character. Awful writing, awful plot, made no narrative sense to the gameplay - just a disaster.