SciFiBoy on 14 July 2009
Gran Turismo 5 imo, has the bigger fanbase (im working under the assumption that most PS3 owners were also PS2 owners) and will probably top 5m and become best selling PS3 game so far.
Forza 3 should be a super game, but it wont be Gran Turismo 5, also, Forza 2 has sold 4m so far, no where near Gran Turismo's expected sales, unless Forza 3 sees a marked increase on 2 in terms of sales, GT5 will win by a fair margin.
so, my answer is, almost certainly GT5, but dont rule Forza 3 out completley.
