GOTY 2010 will most likely be a PS3 exclusive making it three wins in a row. 2008: MGS 4. 2009: Uncharted 2.
2010 will be one of Gran turismo 5, God of War 3, The Last Guardian or Heavy Rain which will win GOTY 2010.
Halo:Reach will be the highest selling title for 2010 and GOTY for the XBox 360 but will not win overall GOTY 2010.
IMHO: FFXIII stands no chance of winning GOTY 2010. We have seen extremely mixed Japanese reviews on that game. Japanese reviewers tend to give the most favourable reviews to games released from their home turf.