If you'd have done some research prior to posting here, you would have realized that your computer is too weak to run Dolphin adequately. Just searching the Hardware forum or checking out the Dolphin wiki would have told you that.
At any rate, you shouldn't compare modern PC games and Dolphin's emulation. They're too different kinds of programs, each with its own demands on hardware. Many games rely on the GPU for their performance, and even machines equipped with mid-range CPUs can get great performance if the GPU is good enough. Dolphin uses the GPU for things like internal resolution, anti-aliasing, and anisotropic filtering. If your GPU is good enough, then most of the remaining performance is reliant on the CPU. However, some PC games are fairly demanding on the CPU, and some games in Dolphin stress the GPU more so than others. Still, PC gaming is not equivalent to Dolphin emulation, so getting high-quality PC gaming does not guarantee good Dolphin performance.
At any rate, you shouldn't compare modern PC games and Dolphin's emulation. They're too different kinds of programs, each with its own demands on hardware. Many games rely on the GPU for their performance, and even machines equipped with mid-range CPUs can get great performance if the GPU is good enough. Dolphin uses the GPU for things like internal resolution, anti-aliasing, and anisotropic filtering. If your GPU is good enough, then most of the remaining performance is reliant on the CPU. However, some PC games are fairly demanding on the CPU, and some games in Dolphin stress the GPU more so than others. Still, PC gaming is not equivalent to Dolphin emulation, so getting high-quality PC gaming does not guarantee good Dolphin performance.