I honestly think that gng is one of the most punishing games ever created. The fact that you complete it (took me till adulthood with cheats) that it turns around and tell you to do it again to actually win, is one of the most evil things that the game could have done.
Finishing Ghost and goblins (along with ghouls and ghosts) without cheats/saves is bragging rights
My ultimate gaming achievement was beating Pulstar on one quarter in the arcade (although it wasn't really fair, I had a neogeo cabinet at home with Pulstar and I played it for hours everyday for weeks). Still, this is an accomplishment that no one I know has matched