Wow, talk about sillyness for several reasons.
Halo is firstly younger, and has less games in the series.
Its also only been on consoles that haven't been anywhere near the market leader (GT had two generations in a row on the market leading console). Halo also had to fight agains the perception that console FPS games were a waste of time compared to their pc bretheren. The perception that pc is the proper platform for fps gaming still persists today and that perception was far far stronger when halo combat evolved first came out.
Not to mean any disrepect to Gran Turismo, which obviously is absolutely massive. But it had more going for it in its early days then Halo did.
Plus GT and Halo are tiny franchises compared to Pokemon, Mario and the Sims (and more recently the wii line of games) anyway, so whats the point of debating about whose the better seller when neither are anywhere close to the top anyway.
