I just run the cpu_benchmark2 with all settings on low (physik particles ... on veryhigh) on 800x600
as you can see it used all four cores but its poorly optimized for quadcores.
When i play games with the Unreal Engine 3 (Bioshock, UT3...) which is fully optimized, all cores are maxed out nearly all the time.
Another thing is that when you play the game, nearly all the time only two cores are used. As you can see above.