You can play some NES games with gpsp with the help of the PocketNES. You can convert the NES ROMs into GBA ROMs with following process.
- Download the PocketNes MenuMaker and PocketNES.gba files into your pc.
- Set the PocketNES.GBA file in the MenuMaker settings
- use the MenuMaker to pach a NES ROM into GBA ROM.
I tested this only with few games, and I know that it works at least on some level with some ROMs. No guarantees 😉
Please do not add NES games to the gpsp compatibility list. It’s primary a GBA emulator after all.