I admit that when I was young and naive I used to enable cheats all the time on Amiga games (via trainers), and I still used to enjoy the games. But after a few years, I realised how much more fun it was to play games without cheating, as they were intended to be played.
Nowadays, I never, ever, cheat on retro or modern games alike. Once you witness how much rewarding, challenging and satisfying games are without cheats, you'll never go back to using them. And I get really annoyed by gamers who seem to think that cheating in games is compulsory, especially if you want to complete them.
What fun is that? Not very much. If such players have to cheat to complete, then they shouldn't go around calling themselves gamers. Because they are not.