Software-wise, sure. It's easy to dump the BIOS and game. The hard part is emulating the hardware. Consoles often have quirky architectures and special chips that don't map to PCs very well. And the chips themselves often have quirks that either aren't documented, or work in a way that disagrees with documentation. But the game developers often relied on those particular quirks for their games. For example, if there was a bug in the GPU that caused textures to become blurry when loaded in a certain way, a developer might exploit that as a free blur filter. (If you're interested in actual examples, try the Dolphin dev blog. I think it's really interesting.)