Here, you will find only links of sites for have correct emulators.

No demand of games (roms), I don't give links.

For NES :

NESticle
Jnes

For SNES :

ZSNES
Snes9x

For N64 :

UltraHLE (French version for the moment).
Nemu64
Project64

For Game Boy :

No$Gmb