this is a tough one, I;m going to go with GT going by this generation of gamer's massive acceptance of GT5P. If you take GT5P's sales and estimate growth of PS3 userbase with GT's fanbase I believe GT5 can surpass GT4's sales. It might even be able to match the original GT's sales.
Halo 3 is massive seller. It is just that as of now its an "old" game. It is a massive seller though and Halo 3: ODST will probably sell about 8 million. It is just that it doesnt have John in it.










