Emulators on PSP

Nintendo

Game Boy Advance

gpSPmod (20090720)* or gpSP-J (20120616)*

*gpSP-J has superior compatibility, gpSPmod has more options for customization (full screen, cheats, etc), both are superior to Kai

Game Boy/Color

GeMP 3.3 or MasterBoy 2.10 

Famicom/Famicom Disc System 

NesterJ 1.13 beta2 or NesterJ AoEX *

*AoEX is based on NesterJ 1.12 Plus 0.61 RM, so it includes features like rewind mode, cheat codes support, rotated/mirrored screen, sepia palette, support to rare mappers (the pirate bootleg FF7 works on it), etc, but it's compatibility is inferior to 1.13 beta2.

Super Famicom (SNES)

Snes9xTYL(me)cm Mod Git* or Snes9xTYL(me)cm Mod R16

*SNES emulation is not that good to begin with, but this is the fastest and most compatible.

SEGA

Genesis/Sega CD 

PicoDrive 1.51b  

Master System/Game Gear 

MasterBoy 2.10 (also compatible with GB and GBC)

Other

PC Engine/CD 

HuE 0.70  

Neo-Geo Pocket

RACE! 2.16-1.0

WonderSwan/Color 

e(mulator) v082f (multi-emulator)

Java

PSPKVM 0.5.5

Arcade

UOcps1psp (CPS1), UOcps2psp (CPS2), UOmvspsp (Neo-Geo), UOncdzpsp (Neo-Geo CD)  

What about PS1 games? 

You have 3 options: 

• download them from Sony servers (registration required)

• convert isos to eboot using PSX2PSP

• download pre-converted games: Devils-Shadow, PSPISO, etc.