If you're Canadian and traded in your old copy of Fallout 3 for the DLC-laden Fallout 3 Game of the Year Edition, you might want to pay attention to some worrying claims on Bethesda's forums. Apparently there were two versions of the original Fallout 3 stocked in Canada, and only one of them produced save games that are compatible with the newly released GotY edition:
Original Fallout 3 save files and game file remain untouched. GOTY creates NEW game and save files (although still named simply "Fallout 3") and will not continue or load an old save. However, it correctly updates the trophy list and does not create a new one. Uh oh.
The game file it creates is much larger (6.7 GB) but does not have a version number. My GOTY is BLUS-30455, but I'm not sure what my original copy was.
From what I can gather, the stores in Canada had two Fallout 3's stocked. One with BLUS-30185 and the other with the serial number BLUS-30234. They're both English language versions, but they aren't compatible. My guess is that the GOTY edition is the same sort of thing. See if you can find a GOTY with a different serial number at the EBGames.