I don't think games and other applications were ever really scaled up to take full advantage of multi threading. We're slowly getting there. Intel has such a huge % of the marketshare of store-bought and prebuilt PCs that *most* programming is centered around 2C, 4T or 4C, 4T processors.
Having 4C, 8T or 6-8C is still quite uncommon, so most companies/programs/games don't really bother scaling up to that factor. When they DO become more common in the future, we'll likely see more games/applications take advantage of it. But right now, and definitely in the future as well, GPUs can handle many, many parallel computations at once, and then squish it all back together. There are many potential uses to harness a GPU's calculation power over the work that even a good CPU can do in the same amount of time.
AMD has done well in the gaming console market, on the other hand. They are very price-competitive and good onboard graphics and core count for consoles. The original Xbox had to make use of an Intel Celeron because then, like now, the higher-end chips were just too expensive to build a console around that people wouldn't complain about the high price.