Well, I've use emulators to refresh memories of my old Atari 2600 games. Also, I've used emulators to play old games like Contra, Super Mario , Double Dragon, Street Fighter (SF I have without emulator too), etc.

Further, I've also used 8085 emulator to try out assembly routines in 8085 instructions.

I love emulators - will try to program a couple soon.