Not sure I agree with the Game of the Year award to Fallout 3. It's a great game but somewhat repetitive in combat and a little too easy later on. The mods will save it, but I don't think that sort of thing should be part of award decision making. Also, carrying twenty guns in a backpack is a little too much for even the hardiest vault dweller if I'm honest, so a little bit of realism in that regard would have been appreciated.
Mind you, given the alternatives, I guess there was nothing that could really compete. 2008 wasn't that great really, looking at the Wikipedia list.
My game of the year would probably be Sins of a Solar Empire, or perhaps Wrath of the Lich King. Fallout 3 would be second, maybe even third on my list.