Just because something is considered "better" doesn't automatically mean it is going to sell better.
Something to consider is cost. The cheapest x360 is much cheaper than a PS3. I consider Ferarri to be better than a Toyota but which sells more...not quite a good analogy but you see my point.
If the PS3 and X360 was exactly the same price for all models then I think it would be far closer.
Then you take into account that the biggest market (NA) favours the X360 above the PS3, which helps generate profits for the X360 as NA is also the biggest software market.
You conveniently ignored the wii, but I think if you had considered it, it will go a long way in answering your overall question.
Meaning why is what is considered the worst spec console killing the opposition even when they too now have motion control.
