It'll almost certainly be game of the year. The only competition is likely to come from MGS 4. It would take something coming from very left field for game of the year to not be one of those two, with GTA IV currently a very strong front runner.
As for best game of all time, its far too subjective a title. There'll never be any consensus. It's worth further noting that the likes of Gamerankings is of no real value in settling this issue. Gamerankings is a largely useless site.







