LocoRoco on PSP has some slowdowns and absolutely maxes out my Pi causing a very quick heat lockup if I don't have the fan on. I would just play it on my actual PSP, but i develop tendon pain after a couple minutes using the PSP anymore.
Enhanced Resolution on the PSX does look great and frankly, if I don't run that or PSP, then I could have stuck with my Pi2. I may try out no enhanced resolution but a shader to see how it runs.
I don't see Dolphin (GC/wii) or the PS2 emulator on a Pi for a long time. It's just not going to be powerful enough on the graphics end. Frankly, I have an XBOX 360 and XBOX One when I want more modern stuff. The X360 still plays a lot of the better original XBOX games.
Heck, my boys are spoiled with their choice of: Xbox 360, Xbox One, PSX, N64, Wii (the version that can play GC games if I bough a GC controller) and Retropie.