Isn't that also due to the reason that consoles, once sold, last for close to 10 years and the game developers have to design their games for sub par hardware.

Isn't that also due to the reason that consoles, once sold, last for close to 10 years and the game developers have to design their games for sub par hardware. Since graphics sell games more, they spend most of their available computation on graphics and other areas rather than coming up with intelligent AI which takes a lot of computation as well. This is probably the reason why we don't have many big single player games.