The PSP as an emulator machine has it's ups and downs. It can play A LOT of different emulators, and some of them very well. But.....
The screen is 16:9. Not the right aspect ratio for these retro games. Also, when the game is moving, you get a considerable amount of smearing of the video image. Then there is the stock D-Pad and buttons.
While some emulators work well, and certain games work well, the emulation can be a bit spotty. Especially with SNES it seems.