Best Emulators and questions

Alright i've played games on emulators, but why do some games not work?
Are there like specific games u gotta play?
Should i get a specicfic emulator?
I was hoping i could play like final fantasy, pokemon, or kh
Just post some answers or questions as you like ;)

Emulators are far from perfect. Some games don't work because the emulator is not perfect.You can play Final Fantasy, Pokemon, and Kingdom Hearts though. As long as your PC is powerful enough.