A PSX2 emulator would be VERY hard to do (I would say impossible except nothing is impossible) because the PSX2 is fundamentally different from a PC in the design.
The PSX2 has a sickly fast bus (the thing that transfer stuff between memory, CPU, DCD, video card etc.). You can't really compare the speed of the PSX2 bus with the PC bus. On the other hand, the PSX2 have 4 MB of graphics memory in total!
On a PC, you usually download all the textures to the memory of your graphics card when the game starts, and use them the rest of the time. On the PSX2, the textures will be pumped over the main system bus each time the textures are needed. There is no way the PC is going to be able to do that. So basically, any emulation would involve rewriting the entire game automatically on the fly...