I can't really remember everything I've played this year, but I'll try and dig out some of the more notable content...
GOTY : Fallout 3 + mods. Despite being my favourite genre, I've only ever played this once, and that was vanilla - around six years ago. Maybe I'm selecting since it's my most recent positive memory.
Honourable mention : Lost Alpha. I found it definitely got better the further I progressed through it, eventually resulting in a good, solid gaming experience. It took a bit of patience / diligence what with the patches / time taken. Quite a slow burner, but I'm glad I persevered.
Most disappointing : I'm really not sure what to put here, but maybe the first Thief game + mods. Although I initially sang some of its praises, I've since come to find the games in general to be not enough to my liking. I do like stealth in some games, but on reflection not as quite as much when it's as heavily weighted as that. I enjoyed the process of modding it though, but overall I found the shine wore off it pretty early on.