As we know, memory subsystem size and speed are very important for contemporary 3D games. Therefore, the obtained results are not surprising at all: Athlon II X4 are far behind their elder brothers from Phenom II X4 family because of the missing L3 cache memory. As a result, even the top Athlon II X4 630 is slightly behind the junior Core 2 Quad CPU.
By the way, the obtained results allow us to make one more very interesting conclusion. Although contemporary gaming applications are better and better optimized for multi-core processors, the triple-core Phenom II X3 looked most preferable in the benchmarks above than the quad-core one.