Heh, while I love technobuffalo's PS3/360 console war videos, they don't really provide you with the knowledge to determine whether Uncharted 2 or GT5P is crunching more numbers than the other.
The bottom line is that the PS3 has a finite amout of raw power. And both Naughty Dog and Polyphony Digital are going to try to get the most out of that finite power. No developer working on a major game is gonna say "Yeah, we're only going to use 2 of the Cell's SPEs because we simply don't need the others". They're going to get the game running, and if they find a way to optimize the game to use less of the CPU, they're going to put the freed power to some new use.
For an example, let's assume Uncharted 2 is a super-optimized game. It's using all of the CPU and there is very little room for any significant optimization. Now, let's assume Polyphony is hard at work on Gran Turismo 5. They're also using all the power that they can draw from the processor to push 16 cars in a race. But alas, they discover a much less processing-intensive way to do something that they do frequently, such as update the physics. A 16 car race which used to need all of the PS3's processing power now only demands half. Does Polyphony let that be that? Or do they put the newly freed processing power to another task? Of course they're going to put the freed power to use. Maybe they'll increase the number of cars per race, or perhaps they'll sprinkle more 3D spectators around the track, or a balanced combination of both.
