I'm super psyched to see how both of these titles do against eachother. No doubt Halo Reach will get off to a strong start. Gamers in the US seem to pick up their copies day one or week one, while here in Europe people seem to have delayed reactions.
and it's clear that GT:5 will outsell Halo Reach in Japan and the EU, so will enough gamers in the US buy enough copies of Halo:Reach to make up and pass out the difference? Another PS3 price drop would also help GT:5 tons, but it's very difficult to predict it's sales, seeing as that fanbase has little representation this gen.
My money's still on GT:5